THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


UNIVERSITY  of  CALIFORNT- 

;''l  i 

LOS  ANGELES 
LIBRARY 


UNIVERSITY  of  CALIFORNIA 

AT 

LOS  ANGELES 
L1BRAJRY 


SAMUEL  W.  JOHNSON,   M.  A. 


HOW  CROPS  GROW. 

A.  TREATISE  ON  THE 

CHEMICAL  COMPOSITION,  STRUCTURE 
AND  LIFE  OF  THE  PLANT, 

FOB  STUDENTS  OF  AGRICULTURE. 


2.  2.  /  3   -5 
BY 

SAMUEL  W.  JOHNSON,  M.  A., 

PROFESSOR  OF  THEORETICAL  AND  AGRICULTURAL  CHEMISTRY  TS  THE  SHOT 

FIELD    SCIENTIFIC   SCHOOL   OF    YALE   UNIVERSITY  ;    DIRECTOR  O» 

THE  CONNECTICUT  AGRICULTURAL  EXPERIMENT   STATION; 

MEMBER  OF  THE  NATIONAL  ACADEMY  OF  SCIENCES. 


StVISED  AND  ENLARGED  EDITiqy. 


OEANGE  JUDD  COMPANY, 

1911 


Entered,  according  to  Act  of  Congress,  In  the  year  1890,  by  the 

ORANGE    JTJDD    COMPANY, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


e  7~^~~-r-^(tXf£l------**Jf-^  r          i  * 


,    g.    A, 


S 

J 


PREFACE. 

The  original  edition  of  this  work,  first  published  in 
1868,  was  the  result  of  studies  undertaken  in  preparing 
instruction  in  Agricultural  Chemistry  which  the  Author 
has  now  been  giving  for  three  and  thirty  years.  To- 
gether with  the  companion  volume,  "How  Crops  Feed," 
it  was  intended  to  present  concisely  but  fully  the  then 
present  state  of  Science  regarding  the  Nutrition  of  the 
higher  Plants  and  the  relations  of  the  Atmosphere, 
Water,  and  the  Soil,  to  Agricultural  Vegetation.  Since 
its  first  appearance,  our  knowledge  of  the  subject  treated 
of  in  the  present  volume  has  largely  participated  in  the 
remarkable  advances  which  have  marked  all  branehes  of 
Science  during  the  last  twenty  years  and  it  has  been  the 
writers'  endeavor  in  this  revised  edition  to  post  the  book 
to  date  as  fully  as  possible  without  greatly  enlarging  its 
bulk  or  changing  its  essential  character.  In  attempting 
to  reach  this  result  he  has  been  doubly  embarassed,  first, 
by  the  great  and  rapidly  increasing  amount  of  recent 
publications  in  which  the  materials  for  revision  must  be 
sought,  and,  second,  by  the  fact  that  official  duties  have 
allowed  very  insufficient  time  for  a  careful  and  compre- 
hensive study  of  the  literature.  In  conclusion,  it  is 
hoped  that  while  the  limits  of  the  book  make  necessary 
the  omission  of  a  multitude  of  interesting  details,  little 
has  been  overlooked  that  is  of  real  importance  to  ;i  fajr 
presentation  of  the  subjects  discussed. 
Ill 


TABLE  OF  CONTENTS. 

INTRODUCTION 1 

DIVISION  I.— CHEMICAL  COMPOSITION  OF  THE  PLANT. 

CHAP.  I.— THE  VOLATILE  PART  OF  PLANTS 12 

§1.  Distinctions  and  Definitions..- 12 

§2.  Elements  of  the  Volatile  Part  of  Plants 14 

63.  Chemical  Affinity 29 

$4.  Vegetable  Organic  Compounds  or  Proximate  Elements  36 

1.  Water 37 

2.  Carbhydrates 39 

3.  Vegetable  Acids 75 

4.  Fats S3 

».  Albuminoids  and  Ferments 87 

6.  Amides 114 

7.  Alkaloids 120 

8.  Phosphorized  Substances 122 

CHAP.  II.— THE  ASH  OF  PLANTS 126 

§  1.  Ingredients  of  the  Ash 126 

Non-metallic   Elements 127 

Carbon  and  its  Compounds 128 

Sulphur  and  its  Compounds 129 

Phosphorus  and  its  Compounds 132 

Chlorine  and  its  Compounds 132 

Silicon  and  its  Compounds 134 

Metallic  Elements 138 

Potassium  and  its  Compounds 138 

Sodium  and  its  Compounds 139 

Calcium  and  its  Compounds 139 

Magnesium  and  its  Compounds 14* 

Iron  and  its  Compounds  141 

Manganese  and  its  Compounds 142' 

Salts 143 

Carbonates  144 

Sulphates 146 

Phosphates 147 

Chlorides 149 

Nitrates 149 

§  2.  Quantity,  Distribution,  and  Variations  of  the  Ash — 151 

Table  of  Proportions  of  Ash  In  Vegetable  Matter — 152 

§  3.  Special  Composition  of  the  Ash  of  Agricultural  Plants  161 

1.  Constant  Ingredients 161 

2.  Uniform  composition  of   normal   specimens  of 

given  plants 161 

Table  of  Ash-analyses 164 

3.  Composition  of  Different  parts  of  Plant 171 

4.  Like  composition  of  similar  plants 173 

6.  Variability  of  ash  of  same  species 174 

6.  What  is  normal  composition  of  the  ash  of  a  plant?  177 

7.  To  what  extent  is  each  ash-ingredient  essential 

or  accidental 18C 

Water-culture 180 

Essential  ash-ingredients 186 

Is  Sodium  Essential  to  Agricultural  Plants  ? 186 

Iron  indispensable 192 

Manganese  unessential 193 

Is  Chlorine  indispensable  ? 194 

Silica  is  not  essential 197 

Ash-ingredients  taken  up  in  excess 201 

Disposition  of  superfluous  matters 203 

State  of  Ash-ingredients  in  plant 207 

6  4.  Functions  of  the  Ash-ingredients 210 

CHAP.  III.— §  1.  Quantitative    Relations  among   the   Ingredients  of 

Plants 220 

52.  Composition  of   the   plant  in  successive  stages  of 

growth 223 

Composition  and  Growth  of  the  Oat  Plant 223 

T 


VI  TABLE  OF  CONTENTS. 


DIVISION  II.— THE  STRUCTURE  OP  THE  PLANT  AND  OFFICES 
OF  ITS  ORGANS. 

CHAP.  I.— GENERALITIES 241 

Organism,  Organs 242 

CHAP.  II.— PRIMARY  ELEMENTS  OF  ORGANIC  STRUCTURE ...243 

§1.  The  Vegetable  Cell 243 

§  2.  Vegetable  Tissues 254 

CHAP.  III.— VEGETATIVE    ORGANS 256 

§  1.  The  Root 256 

Offices  of  Root 260 

Apparent  Search  for  Food 263 

Contact  of  Roots  with  Soil 266 

Absorption  by  Root 269 

Soil  Roots,  Water  Roots,  Air  Roots 273 

§2.  The  Stem .282 

Buds 283 

Layers,  Tillering 286 

Root-stocks '. 287 

Tubers 288 

Structure  of  the  Stem... 289 

Endogenous  Plants 290 

Exogenous  Plants 296 

Sieve-cells 303 

§  3.  Leaves 306 

Leaf  Pores 309 

Exhalation  of  Water  Vapor 311 

Offices  of  Foliage 314 

CHAP.  IV.— REPRODUCTIVE  ORGANS 315 

§1.  The  Flower 316 

Fertilization 319 

Hybridizing 324 

Species.     Varieties 326 

§2.  Fruit 330 

Seed 332 

Embryo 333 

§  3.  Vitality  of  -seeds  and  their  influence  on  the  Plants 

they  produce 335 

Duration  of  Vitality 335 

Use  of  old  and  unripe  seeds 338 

Density  of  seeds 339 

Absolute  weight  of  seeds 340 

Signs  of  Excellence 345 

Ancestry.    Race- vigor 346 

DIVISION  III.— LIFE  OF  THE  PLANT. 
CHAP.  1.— GERMINATION 349 

§  1.  Introductory , 349 

§  2.  Phenomena  of  Germination 350 

§  3.  Conditions  of  Germination 351 

Proper  Depth  of  Sowing 355 

§  4.  Chemical  Physiology  of  Germination 357 

Chemistry  of  Malt 358 

CHAP.  II. — §  1.  Food  of  the  Plant  when  independent  of  the  Seed 366 

§  2.  The  Juices  of  the  Plant.  Their  Nature  and  Movements369 

Flow  of  Sap 370 

Composition  of  Sap 376 

Kinds  of  Sap.  378 

Motion  of  Nutrient  Matters 379 

§3.  Causes  of  Motion  of  the  Juices 385 

Porosity  of  Tissues 385 

Imbibition 386 

Liquid  Diffusion 390 

Osmose  or  Membrane  Diffusion 393 

Root   Action ...  399 

Selective  Power  of  Plant 401 

§  4.  Mechanical  effects  of  Osmose 406 

APPENDIX. 
TABLE.— Composition  of  Agricultural  Products 409 


HOW  CROPS  GROW. 

2.2/33 

INTRODUCTION. 


The  object  of  agriculture  is  the  production  of  certain 
plants  and  certain  animals  which  are  employed  to  feed, 
clothe  and  otherwise  serve  the  human  race.  The  first 
aim,  in  all  cases,  is  the  production  of  plants. 

Nature  has  made  the  most  extensive  provision  for  the 
spontaneous  growth  of  an  immense  variety  of  vegetation  ; 
but  in  those  climates  where  civilization  most  certainly 
attains  its  fullest  development,  man  is  obliged  to  employ 
art  to  provide  himself  with  the  kinds  and  quantities  of 
vegetable  produce  which  his  necessities  or  luxuries  de- 
mand. In  this  defect,  or,  rather,  neglect  of  nature,  ag- 
riculture has  its  origin. 

The  art  of  agriculture  consists  in  certain  practices  and 
operations  which  have  gradually  grown  out  of  an  obser- 
vation and  imitation  of  the  best  efforts  of  nature,  or  have 
been  hit  upon  accidentally,  or,  finally,  have  been  deduced 
from  theory. 

The  science  of  agriculture  is  the  rational  theory  and 
systematic  exposition  of  the  successful  art. 

Strictly  considered,  the  art  and  science  of  agriculture 
are  of  equal  age,  and  have  grown  together  from  the  ear- 


2  HOW  CROPS  GROW. 

liest  times.  Those  who  first  cultivated  the  soil  by  dig- 
ging, planting,  manuring  and  irrigating,  had  their  suffi- 
cient reason  for  every  step.  In  all  cases,  thought  goes 
before  work,  and  the  intelligent  workman  always  has  a 
theory  upon  which  his  practice  is  planned.  No  farm 
was  ever  conducted  without  physiology,  chemistry,  and 
physics,  any  more  than  an  aqueduct  or  a  railway  was  ever 
built  without  mathematics  and  mechanics.  Every  suc- 
cessful farmer  is,  to  some  extent,  a  scientific  man.  Let 
him  throw  away  the  knowledge  of  facts  and  the  knowl- 
edge of  principles  which  constitute  his  science,  and  he 
has  lost  the  elements  of  his  success.  The  farmer  without 
his  reasons,  his  theory,  his  science,  can  have  no  plan; 
and  these  wanting,  agriculture  would  be  as  complete  a 
failure  with  him  as  it  would  be  with  a  man  of  mere 
science,  destitute  of  manual,  financial  and  executive  skill. 

Other  qualifications  being  equal,  the  more  advanced 
and  complete  the  theory  of  which  the  farmer  is  the  mas- 
ter, the  more  successful  must  be  his  farming.  The  more 
he  knows,  the  more  he  can  do.  The  more  deeply,  com- 
prehensively, and  clearly  he  can  think,  the  more  econ- 
omically and  advantageously  can  he  work. 

That  there  is  any  opposition  or  conflict  between  science 
and  art,  between  theory  and  practice,  is  a  delusive  error. 
They  are,  as  they  ever  have  been  and  ever  must  be,  in  the 
fullest  harmony.  If  they  appear  to  jar  or  stand  in  con- 
tradiction, it  is  because  we  have  something  false  or  incom- 
plete in  what  we  call  our  science  or  our  art ;  or  else  we  do 
not  perceive  correctly,  but  are  misled  by  the  narrowness 
and  aberrations  of  our  vision.  It  is  often  said  of  a  ma- 
chine, that  it  was  good  in  theory,  but  failed  in  practice. 
This  is  as  untrue  as  untrue  can  be.  If  a  machine  has 
failed  in  practice,  it  is  because  it  was  imperfect  in  theory. 
It  should  be  said  of  such  a  failure — the  machine  was 
good,  judged  by  the  best  theory  known  to  its  inventor, 
but  its  incapacity  to  work  demonstrates  that  the  theory 
had  a  flaw* 


ttftBODUCTIOK.  3 

But,  although  art  and  science  are  thus  inseparable,  it 
must  not  be  forgotten  that  their  growth  is  not  altogether 
parallel.  There  are  facts  in  art  for  which  science  can,  as 
yet,  furnish  no  adequate  explanation.  Art,  though  no 
older  than  science,  grew  at  first  more  rapidly  in  vigor 
and  in  stature.  Agriculture  was  practiced  hundreds  and 
thousands  of  years  ago,  with  a  success  that  does  not  com- 
pare unfavorably  with  ours.  Nearly  all  the  essential 
points  of  modern  cultivation  were  regarded  by  the  Ro- 
mans before  the  Christian  era.  The  annals  of  the  Chi- 
nese show  that  their  wonderful  skill  and  knowledge  were 
in  use  at  a  vastly  earlier  date. 

So  much  of  science  as  can  be  attained  through  man's 
unaided  senses,  reached  considerable  perfection  early  in 
the  world's  history.  But  that  part  of  science  which  re- 
lates to  things  invisible  to  the  unassisted  eye,  could  not 
be  developed  until  the  telescope  and  the  microscope  had 
been  invented,  until  the  increasing  experience  of  man  and 
his  improved  art  had  created  and  made  cheap  the  other 
inventions  by  whose  aid  the  mind  can  penetrate  the  veil 
of  nature.  Art,  guided  at  first  by  a  very  crude  and  im- 
perfectly-developed science,  has,  within  a  comparatively 
recent  period,  multiplied  those  instruments  and  means  of 
research  whereby  science  has  expanded  to  her  present 
proportions. 

The  progress  of  agriculture  is  the  joint  work  of  theory 
and  practice.  In  many  departments  great  advances  have 
been  made  during  the  last  hundred  years ;  especially  is 
this  true  in  all  that  relates  to  implements  and  machines, 
and  to  the  improvement  of  domestic  animals.  It  is, 
however,  in  just  these  departments  that  an  improved 
theory  has  had  sway.  More  recent  is  the  development  of 
agriculture  in  its  chemical  and  physiological  aspects.  In 
these  directions  the  present  century,  or  we  might  almost 
say  the  last  fifty  years,  has  seen  more  accomplished  than 
all  previous  time. 


4  HOW  CROPS  GEOW. 

The  first  book  in  the  English  language  on  the  subjects 
which  occupy  a  good  part  of  the  following  pages,  was 
written  by  a  Scotch  nobleman,  the  Earl  of  Dundonald, 
and  was  published  at  London  in  1795.  It  is  entitled: 
"A  Treatise  showing  the  Intimate  Connection  that  sub- 
sists between  Agriculture  and  Chemistry."  The  learned 
Earl,  in  his  Introduction,  remarked  that  "  the  slow  pro- 
gress which  agriculture  has  hitherto  made  as  a  science  is 
to  be  ascribed  to  a  want  of  education  on  the  part  of  the 
cultivators  of  the  soil,  and  the  want  of  knowledge  in  such 
authors  as  have  written  on  agriculture  of  the  intimate 
connection  that  subsists  between  the  science  and  that  of 
chemistry.  Indeed,  there  is  no  operation  or  process,  not 
merely  mechanical,  that  does  not  depend  on  chemistry, 
which  is  defined  to  be  a  knowledge  of  the  properties  of 
bodies,  and  of  the  effects  resulting  from  their  different 
combinations. "  Earl  Dundonald  could  not  fail  to  see  that 
chemistry  was  ere  long  to  open  a  splendid  future  for  the 
ancient  art  that  always  had  been  and  always  is  to  be  the 
prime  support  of  the  nations.  But  when  he  wrote,  how 
feeble  was  the  light  that  chemistry  could  throw  upon  the 
fundamental  questions  of  agricultural  science !  The 
chemical  nature  of  atmospheric  air  was  then  a  discovery 
of  barely  twenty  years'  standing.  The  composition  of 
water  had  been  known  but  twelve  years.  The  only  ac- 
count of  the  composition  of  plants  that  Earl  Dundonald 
could  give  was  the  following:  "Vegetables  consist  of 
mucilaginous  matter,  resinous  matter,  matter  analogous 
to  that  of  animals,  and  some  proportion  of  oil.  *  * 
Besides  these,  vegetables  contain  earthy  matters,  formerly 
held  in  solution  in  the  newly-taken-in  juices  of  the 
growing  vegetable."  He  further  explains  by  mentioning 
on  subsequent  pages  that  starch  belongs  to  the  mucil- 
aginous matters,  and  that,  on  analysis  by  fire,  vegetables 
yield  soluble  alkaline  salts  and  insoluble  phosphate  of 
lime.  But  these  salts,  he  held,  were  formed  in  the  pro* 


INTRODUCTIOH.  5 

cess  of  burning,  their  lime  excepted,  and  the  fact  of  their 
being  taken  from  the  soil  and  constituting  the  indispen- 
sable food  of  plants,  his  Lordship  was  unacquainted  with. 
The  gist  of  agricultural  chemistry  with  him  was,  that 
plants  are  "  composed  of  gases  with  a  small  proportion  of 
calcareous  matter;"  for  "  although  this  discovery  may 
appear  to  be  of  small  moment  to  the  practical  farmer,  yet 
it  is  well  deserving  of  his  attention  and  notice,  as  it 
throws  great  light  on  the  nature  and  food  of  vegetables." 
The  fact  being  then  known  that  plants  absorb  carbonic 
acid  from  the  air,  and  employ  its  carbon  in  their  growth, 
the  theory  was  held  that  fertilizers  operate  by  promoting 
the  conversion  of  the  organic  matter  of  the  soil  or  of 
composts  into  gases,  or  into  soluble  humus,  which  were 
considered  to  be  the  food  of  plants. 

The  first  accurate  analysis  of  a  vegetable  substance  was 
not  accomplished  until  fifteen  years  after  the  publication 
of  Dundonald's  Treatise,  and  another  like  period  passed 
before  the  means  of  rapidly 'multiplying  good  analyses 
had  been  worked  out  by  Liebig.  So  late  as  1838,  the  Got- 
tingen  Academy  offered  a  prize  for  a  satisfactory  solution 
of  the  then  vexed  question  whether  the  ingredients  of 
ashes  are  essential  to  vegetable  growth.  It  is,  in  fact, 
during  the  last  fifty  years  that  agricultural  chemistry  has 
come  to  rest  on  sure  foundations.  Our  knowledge  of  the 
structure  and  physiology  of  plants  is  of  like  recent  devel- 
opment. What  immense  practical  benefit  the  farmer  has 
gathered  from  this  advance  of  science  !  Chemistry  has 
ascertained  what  vegetation  absolutely  demands  for  its 
growth,  and  points  out  a  multitude  of  sources  whence 
the  requisite  materials  for  crops  can  be  derived.  Cato 
and  Columella  knew  indeed  that  ashes,  bones,  bird- 
dung  and  green  manuring,  as  well  as  drainage  and  aera- 
tion of  the  soil,  were  good  for  crops ;  but  that  carbonic 
acid,  potash,  phosphate  of  lime,  and  compounds  of  nitro- 
gen are  the  chief  pabulum  of  vegetation,  they  did  not 


0  HOW  CROPS  GROW. 

know.  They  did  not  know  that  the  atmosphere  dissolves 
the  rocks,  and  converts  inert  stone  into  nutritive  soil. 
These  grand  principles,  understood  in  many  of  their  de- 
tails, are  an  inestimable  boon  to  agriculture,  and  intelli- 
gent farmers  have  not  been  slow  to  apply  them  in  prac- 
tice. The  vast  trade  in  phosphatic  and  Peruvian  guano, 
and  in  nitrate  of  soda ;  the  great  manufactures  of  oil  of 
vitriol,  of  superphosphate  of  lime,  of  fish  fertilizers ;  and 
the  mining  of  fossil  bones  and  of  potash  salts,  are  indus- 
tries largely  or  entirely  based  upon  and  controlled  by 
chemistry  in  the  service  of  agriculture. 

Every  day  is  now  the  witness  of  new  advances.  The 
means  of  investigation,  which,  in  the  hands  of  the  scien- 
tific experimenter,  have  created  within  the  writer's  mem- 
ory such  arts  as  photography  and  electro-metallurgy,  and 
have  produced  the  steam-engine,  the  telegraph,  the  tele- 
phone and  the  electric  light,  are  working  and  shall  ever- 
more continue  to  work  progress  in  the  art  of  agriculture. 
This  improvement  will  not  consist  so  much  in  any  re- 
markable discoveries  that  shall  enable  us  to  "grow  two 
blades  of  grass  where  but  one  grew  before;"  but  in  the 
gradual  disclosure  of  the  reasons  of  that  which  we  have 
long  known,  or  believed  we  knew ;  in  the  clear  separa- 
tion of  the  true  from  the  seemingly  true,  and  in  the  ex- 
change of  a  wearying  uncertainty  for  settled  and  positive 
knowledge. 

It  is  the  boast  of  some  who  affect  to  glory  in  the  suf- 
ficiency of  practice  and  decry  theory,  that  the  former  is 
based  upon  experience,  which  is  the  only  safe  guide.  But 
this  is  a  one-sided  view  of  the  matter.  Theory  is  also 
based  upon  experience,  if  it  be  worth  the  name.  The 
fancies  of  an  ignorant  and  undisciplined  mind  are  not 
theory  as  that  term  is  properly  understood.  Theory,  in 
the  strict  scientific  sense,  is  always  a  deduction  from, 
facts,  and  the  best  deduction  of  which  the  stock  of  facts 
in  our  possession  admits.  It  is  therefore  also  the  inter* 


INTKODUCTION.  7 

pretation  of  facts.  It  is  the  expression  of  the  ideas  which 
facts  awaken  when  submitted  to  a  fertile  imagination  and 
well-balanced  judgment.  A  scientific  theory  is  intended 
for  the  nearest  possible  approach  to  the  truth.  Theory 
is  confessedly  imperfect,  because  our  knowledge  of  facts 
is  incomplete,  our  mental  insight  weak,  and  our  judg- 
ment fallible.  But  the  scientific  theory  which  is  framed 
by  the  contributions  of  a  multitude  of  earnest  thinkers 
and  workers,  among  whom  are  likely  to  be  the  most  gifted 
intellects  and  most  skillful  hands,  is,  in  these  days,  to  a 
great  extent  worthy  of  the  Divine  truth  in  nature,  of 
which  it  is  the  completest  human  conception  and  ex- 
pression. 

Science  employs,  in  effecting  its  progress,  essentially 
the  same  methods  that  are  used  by  merely  practical  men. 
Its  success  is  commonly  more  rapid  and  brilliant,  because 
its  instruments  of  observation  are  finer  and  more  skill- 
fully handled  ;  because  it  experiments  more  industriously 
and  variedly,  thus  commanding  a  wider  and  more  fruit- 
ful experience  ;  because  it  usually  brings  a  more  culti- 
vated imagination  and  a  more  disciplined  judgment  to 
bear  upon  its  work.  The  devotion  of  a  life  to  discovery 
or  invention  is  sure  to  yield  greater  results  than  a  desul- 
tory application  made  in  the  intervals  of  other  absorbing 
pursuits.  It  is  then  for  the  interest  of  the  farmer  to 
avail  himself  of  the  labors  of  the  man  of  science,  when 
the  latter  is  willing  to  inform  himself  in  the  details  of 
practice,  so  as  rightly  to  comprehend  the  questions  which 
press  for  a  solution. 

Agricultural  science,  in  its  widest  scope,  comprehends 
a  vast  range  of  subjects.  It  includes  something  from 
nearly  every  department  of  human  learning.  The  natu- 
ral sciences  of  geology,  meteorology,  mechanics,  physics, 
chemistry,  botany,  zoology  and  physiology,  are  most  in- 
timately related  to  it.  It  is  not  less  concerned  with  so- 
cial and  political  economy.  In  this  treatise  it  will  not  be 


8  HOW  CROPS  GROW. 

attempted  to  touch,  much  less  cover,  all  this  ground,  but 
some  account  will  be  given  of  certain  subjects  whose  un- 
derstanding will  be  of  the  most  direct  service  to  the  agri- 
culturist. The  Theory  of  Agriculture,  as  founded  on 
chemical,  physical  and  physiological  science,  in  so  far  as 
it  relates  to  the  Chemical  Composition,  the  Structure  and 
the  Life  of  the  Plant,  is  the  topic  of  this  volume. 

Some  preliminary  propositions  and  definitions  may  be 
serviceable  to  the  reader. 

Science  deals  with  Matter  and  Force. 

Matter  is  that  which  has  weight  and  bulk. 

Force  is  the  cause  of  changes  in  matter — it  is  appre- 
ciable only  by  its  effects  upon  matter. 

Force  resides  in  and  is  inseparable  from  matter. 

Force  manifests  itself  in  motion  and  change. 

All  matter  is  perpetually  animated  by  force — is  there- 
fore never  at  rest.  What  we  call  rest  in  matter  is  simply 
motion  too  fine  for  our  perceptions. 

The  different  kinds  of  matter  known  to  science  have 
been  resolved  into  some  seventy  chemical  elements  or  sim- 
ple substances. 

The  elements  of  chemistry  are  forms  of  matter  which 
have  thus  far  resisted  all  attempts  at  their  simplification 
or  decomposition. 

In  ordinary  life  we  commonly  encounter  but  twelve 
kinds  of  matter  in  their  elementary  state,  viz. : 

Oxygen,  Carbon,  Mercury,  Tin, 

Nitrogen,  Iron,  Copper,  Silver, 

Sulphur,  Zinc,  Lead,  Gold. 

The  numberless  other  substances  with  which  we  arc 
familiar,  are  mostly  compounds  of  the  above,  or  of  twelve 
other  elements,  viz. : 

Hydrogen,         Silicon,  Calcium,  Manganese, 

Phosphorus,       Potassium,          Magnesium,       Chromium, 
Chlorine,  Sodium,  Aluminum,       Nickelt 


INTRODUCTION. 


So  far  as  human  agency  goes,  these  chemical  elements 
are  indestructible  as  to  quantity,  and  not  convertible 
one  into  another. 

We  distinguish  various  natural  manifestations  of  force 
which,  acting  on  or  through  matter,  produce  all  material 
phenomena.  In  the  subjoined  scheme  the  recognized 
forces  are  to  some  extent  classified  and  defined,  in  a  man- 
ner that  may  prove  useful  to  the  reader. 


-     Repulsive 

\  Att™ctive 

distances     I 


Act  only  at 
insensible 
distances 


Attractive 


HEA?                     }  Radiant 

ELECTRICITY           »  inductive 
MAGNETISM                   j"3 

GRAVITATION           Cosmical 

•Physical 

COHESION 

CRYSTALLIZATION 

ADHESION 

SOLUTION 

^-Molecular 

OSMOSE 

AFFINITY 

Atomic         Chemical 

VITALITY                    Organic         Biological 

Within  human  experience  the  different  kinds  of  force 
are  mostly  convertible  each  into  the  others,  and  must 
therefore  be  regarded  as  fundamentally  one  and  the  same. 
Force,  like  matter,  is  indestructible.  Force  acting  on 
a  body  may  either  increase  its  Kinetic  Energy,  or  be 
stored  up  in  it  as  Potential  Energy.  Kinetic  (or  ac- 
tual) energy  is  the  energy  of  a  moving  body.  Potential 
(or  possible)  energy  is  the  energy  which  a  body  may  be 
able  to  exert  because  of  its  state  or  position.  A  falling 
stone  or  running  clock  gives  out  actual  energy.  The 
stone  while  being  raised,  or  the  clock  while  winding,  ac- 
quires and  stores  potential  energy.  In  a  similar  manner 
kinetic  solar  energy,  reaching  the  earth  as  light,  heat  and 
chemical  force,  not  only  sets  in  operation  the  visible  ac- 
tivities of  plants,  but  accumulates  in  them  a  store  of  po- 
tential energy  which,  when  they  serve  as  food  or  fuel,  re- 
appears as  kinetic  energy  in  the  forms  of  animal  heat, 
muscular  and  uervous  activity,  or  as  fire  and  light. 

The  sciences  that  more  immediately  relate  to  agricult- 
ure we  Physics,  Chemistry  and  Biology. 


10  HOW  CROPS  GROW. 

Physics,  or  "natural  philosophy,"  is  the  science 
which  considers  the  general  properties  of  matter  and  such 
phenomena  as  are  not  accompanied  by  essential  change 
in  its  obvious  qualities.  All  the  forces  in  the  preceding 
scheme,  save  the  last  two,  manifest  themselves  through 
matter  without  destroying  or  masking  the  matter  itself. 
Iron  may  be  hot,  luminous,  or  magnetic,  may  fall  to  the 
ground,  be  melted,  welded,  and  crystallized ;  but  it  re- 
mains iron,  and  is  at  once  recognized  as  such.  The  forces 
whose  play  does  not  disturb  the  evident  characters  of  sub- 
stances are  physical. 

Chemistry  is  the  science  which  studies  the  proper- 
ties peculiar  to  the  various  kinds  of  matter,  and  those 
phenomena  which  are  accompanied  by  a  fundamental 
change  in  the  matter  acted  on.  Iron  rusts,  wood  burns, 
and  both  lose  all  the  external  characters  that  serve  for 
their  identification.  They  are,  in  fact,  converted  into 
other  substances.  Chemical  attraction,  affinity,  or  chem- 
ism,  as  it  is  variously  termed,  unites  two  or  more  ele- 
ments into  compounds,  unites  compounds  together  into 
more  complex  compounds ;  and,  under  the  influence  of 
heat,  light,  and  other  agencies,  is  annulled  or  overcome, 
so  that  compounds  resolve  themselves  into  simpler  com- 
binations or  into  their  elements.  Chemistry  is  the  science 
of  composition  and  decomposition  ;  it  considers  the  laws 
and  results  of  affinity. 

Biology,  or  physiology,  unfolds  the  laws  of  the 
propagation,  development,  sustenance,  and  death  of  liv- 
ing organisms,  both  plants  and  animals. 

When  we  assert  that  the  object  of  agriculture  is  to  de- 
velop from  the  soil  the  greatest  possible  amount  of  cer- 
tain kinds  of  vegetable  and  animal  produce  at  the  least 
cost,  we  suggest  the  topics  which  are  most  important  for 
the  agriculturist  to  understand. 

The  farmer  deals  with  the  plant,  with  the  soil,  with 
manures,  These  stand  in  close  relation  to  each  other, 


INTRODUCTION.  11 

and  to  the  atmosphere  which  constantly  surrounds  and 
acts  upon  them.  How  the  plant  grows, — the  conditions 
under  which  it  flourishes  or  suffers  detriment, — the  ma- 
terials of  which  it  is  made, — the  mode  of  its  construction 
and  organization, — how  it  feeds  upon  the  soil  and  air, — 
how  it  serves  as  food  to  animals, — how  the  air,  soil, 
plant,  and  animal  stand  rel?ted  to  each  other  in  a  per- 
petual round  of  the  most  beautiful  and  wonderful  trans- 
formations,— these  are  some  of  the  grand  questions  that 
come  before  us  ;  and  they  are  net  less  interesting  to  the 
philosopher  or  man  of  culture,  than  important  to  the 
farmer  who  depends  upon  their  practical  solution  for  his 
comfort ;  or  to  the  statesman,  who  regards  them  in  their 
bearings  upo^  *he  weightiest  of  political  considerations. 


DIVISION   1. 

CHEMICAL    COMPOSITION  OF    THE    PLANT. 

CHAPTER  1. 

THE  VOLATILE  PART  OF  PLANTS. 

V     1* 

DISTINCTIONS   AND   DEFINITIONS. 

OKGANIC  AND  INORGANIC  MATTER.  —All  matter  may 
be  divided  into  two  great  classes — Organic  and  Inorganic. 

Organic  matter  is  the  product  of  growth,  or  of  vital 
organization,  whether  vegetable  or  animal.  It  is  mostly 
combustible,  i.  e.,  it  may  be  easily  set  on  fire,  and  burns 
away  into  invisible  gases.  Organic  matter  either  itself 
constitutes  the  organs  of  life  and  growth,  and  has  a  pecu- 
liarly organized  structure,  inimitable  by  art, — is  made  up 
of  cells,  tubes  or  fibres  (wood  and  flesh) ;  or  else  is  a 
mere  result  or  product  of  the  vital  processes,  and  desti- 
tute of  this  structure  (sugar  and  fat). 

All  matter  which  is  not  a  part  or  product  of  a  living 
organism  is  inorganic  or  mineral  matter  (rocks,  soils, 
water,  and  air).  Most  of  the  naturally-occurring  forms 
of  inorganic  matter  which  directly  concern  agricultural 
chemistry  are  incombustible,  and  destitute  of  anything 
like  organic  structure. 

By  the  processes  of  combustion  and  decay,   organic 
matter  is  disorganized  or  converted  into  inorganic  matter, 
while,  on  the  contrary,  by  vegetable  growth  inorganic 
matter  is  organized,  and  becomes  organic,. 
13 


14  HOW  CROPS  GROW. 

Organic  matters  are  in  general  characterized  by  com- 
plexity of  constitution,  and  are  exceedingly  numerous 
and  various ;  while  inorganic  bodies  are  of  simpler  com- 
position, and  comparatively  few  in  number. 

VOLATILE  AND  FIXED  MATTER. — All  plants  and  ani- 
mals, taken  as  a  whole,  and  all  of  their  organs,  consist  of 
a  volatile  and  fixed  part,  which  may  be  separated  by 
burning ;  the  former — usually  by  far  the  larger  share — 
passing  into  and  mingling  with  the  air  as  invisible  gases  ; 
the  latter — forming,  in  general,  but  from  one  to  five  per 
cent,  of  the  whole — remaining  as  ashes. 

EXPERIMENT  1. — A  splinter  of  wood  heated  in  the  flame  of  a  lamp 
takes  fire,  burns,  and  yields  volatile  matter,  which  consumes  with  flame, 
and  ashes,  which  are  the  only  visible  residue  of  the  combustion. 

Many  organic  bodies,  products  of  life,  but  not  essential 
vital  organs,  as  sugar,  citric  acid,  etc.,  are  completely 
volatile  when  in  a  state  of  purity,  and  leave  no  ash. 

USE  OF  THE  TERMS  ORGANIC  AND  INORGANIC. — It  is 
usual  among  agricultural  writers  to  confine  the  term  or- 
ganic to  the  volatile  or  destructible  portion  of  vegetable 
and  animal  bodies,  and  to  designate  their  ash-ingredients 
as  inorganic  matter.  This  is  not  an  entirely  accurate 
distinction.  What  is  found  in  the  ashes  of  a  tree  or  of  a 
seed,  in  so  far  as  it  was  an  essential  part  of  the  organism, 
was  as  truly  organic  as  the  volatile  portion,  and,  by  sub- 
mitting organic  bodies  to  fire,  they  may  be  entirely  con- 
verted into  inorganic  matter,  the  volatile  as  well  as  the 
fixed  parts. 

ULTIMATE  ELEMENTS  THAT  CONSTITUTE  THE  PLANT.— 
Chemistry  has  demonstrated  that  the  volatile  and  de- 
structible part  of  organic  bodies  is  chiefly  made  up  of  four 
substances,  viz. :  carbon,  oxygen,  hydrogen,  and  nitrogen, 
and  contains  two  other  elements  in  lesser  quantity,  viz. : 
sulphur  and  phosphorus.  In  the  ash  we  may  find  phos- 
phorus, sulphur,  silicon,  chlorine,  potassium,  sodium,  cal- 


TEE  VOLATILE  PART  OP  PLAKTS.  15 

cium,  magnesium,  iron,  and  manganese,  as  well  as  oxy- 
gen, carbon,  and  nitrogen.* 

These  fourteen  bodies  are  elements,  which  means,  in 
chemical  language,  that  they  cannot  be  resolved  into 
other  substances.  All  the  varieties  of  vegetable  and  ani- 
mal matter  are  compounds, — are  composed  of  and  may  be 
resolved  into  these  elements. 

The  above-named  elements  being  essential  to  the  or- 
ganism of  every  plant  and  animal,  it  is  of  the  highest  im- 
portance to  make  a  minute  study  of  their  properties, 


2. 


ELEMENTS  OF  THE  VOLATILE  PART  OF  PLANTS. 

For  the  sake  of  convenience  we  shall  first  consider  the 
elements  which  constitute  the  combustible  part  of  plants, 
viz. : 

Carbon,  Nitrogen,  Sulphur, 

Oxygen,  Hydrogen,  Phosphorus. 

The  elements  which  belong  exclusively  to  the  ash  will 
be  noticed  in  a  subsequent  chapter. 

Carbon,  in  the  free  state,  is  a  solid.  "We  are  familiar 
with  it  in  several  forms,  as  lamp-black,  charcoal,  black- 
lead,  and  diamond.  Notwithstanding  the  substances 
just  named  present  great  diversities  of  appearance  and 
physical  characters,  they  are  identical  in  a  certain  chem- 
ical sense,  as  by  burning  they  all  yield  the  same  product, 
viz. :  carbonic  acid  gas,  also  called  carbon  dioxide. 

That  carbon  constitutes  a  large  part  of  plants  is  evi- 
dent from  the  fact  that  it  remains  in  a  tolerably  pure 
state  after  the  incomplete  burning  of  wood,  as  is  illus- 
trated in  the  preparation  of  charcoal. 


*  Rarely,  or  to  a  slight  extent,  lithium,  rubidium,  iodine,  bromine, 
fluorine,  barium,  copper,  zinc,  titanium,  and  boron. 


16  SOW  CEOPS  GROW. 

EXP.  1. — If  a  splinter  of  dry  pine  wood  be  set  on  fire  and  the  burning 
end  be  gradually  passed  into  the  mouth  of  a  narrow  tube  (see  figure  1), 
whereby  the  supply  of  air  is  cut  off,  or  if  it  be  thrust  into 
sand,  the  burning  is  incomplete,  and  a  stick  of  charcoal  re- 
mains. 

Carbonization  and  Charring  are  terms  used  to 
express  the  blackening  of  organic  bodies  by  heat, 
and  are  due  to  the  separation  of  carbon  in  the  free 
or  uncombined  state. 

The  presence  of  carbon  in  animal  matters  also  is 
shown  by  subjecting  them  to  incomplete  com- 
bustion. 

EXP.  3.— Hold  a  knife-blade  in  the  flame  of  a  tallow  candle ; 
the  full  access  of  air  is  thus  prevented,— a  portion  of  carbon  „.     - 
escapes  combustion,  and  is  deposited  on  the  blade  in  the  form       °*    " 
of  lamp-black. 

Oil  of  turpentine  and  petroleum  (kerosene)  contain  so 
much  carbon  that  a  portion  ordinarily  escapes  in  the  free 
state  as  smoke,  when  they  are  set  on  fire. 

When  bones  are  strongly  heated  in  closely-covered  iron 
pots,  until  they  cease  yielding  any  vapors,  there  remains 
in  the  vessels  a  mixture  of  impure  carbon  with  the  earthy 
matter  (phosphate  of  lime)  of  the  bones,  which  is  largely 
used  in  the  arts,  chiefly  for  refining  sugar,  but  also  in  the 
manufacture  of  fertilizers  under  the  name  of  animal  char- 
coal, or  bone-black. 

Lignite,  bituminous  coal,  anthracite,  coke — the  porous, 
hard,  and  lustrous  mass  left  when  bituminous  coal  is 
heated  with  a  limited  access  of  air,  and  the  metallic  ap- 
pearing gas-carbon  that  is  found  lining  the  iron  cylinders 
in  which  illuminating  coal-gas  is  prepared,  all  consist 
largely  or  chiefly  of  carbon.  They  usually  contain  more 
or  less  incombustible  matters,  as  well  as  a  little  oxygen, 
hydrogen,  nitrogen,  and  sulphur. 

The  different  forms  of  carbon  possess  a  greater  or  less 
degree  of  porosity  and  hardness,  according  to  their  origin 
and  the  temperature  at  which  they  are  prepared. 

Carbon,  in  most  of  its  forms,  is  extremely  indestructi- 


THE  VOLATILE  PAET  OF  PLANTS.  17 

ble  under  ordinary  circumstances.  Hence  stakes  and 
fence  posts,  if  charred  before  setting  in  the  ground,  last 
much  longer  than  when  this  treatment  is  neglected. 

The  porous  varieties  of  carbon,  especially  wood  char- 
coal and  bone-black,  have  a  remarkable  power  of  absorb- 
ing gases  and  coloring  matters,  which  is  taken  advantage 
of  in  the  refining  of  sugar.  They  also  destroy  noisome 
odors,  and  are  used  for  purposes  of  disinfection. 

Carbon  is  the  characteristic  ingredient  of  all  organic 
compounds.  There  is  no  single  substance  that  is  the  ex- 
clusive result  of  vital  organization,  no  ingredient  of  the 
animal  or  vegetable  produced  by  their  growth,  that  does 
not  contain  this  element. 

Oxygen. — Carbon  is  a  solid,  and  is  recognized  by  our 
senses  of  sight  and  feeling.  Oxygen,  on  the  other  hand, 
is  an  air  or  gas,  invisible,  odorless,  tasteless,  and  not  dis- 
tinguishable in  any  way  from  ordinary  air  by  the  unas- 
sisted senses. 

It  exists  in  the  free  (uncombined)  state  in  the  atmos- 
phere we  breathe,  but  there  is  no  means  of  obtaining  it 
pure  except  from  some  of  its  compounds.  Many  metals 
unite  readily  with  oxygen,  forming  compounds  (oxides) 
which  by  heat  separate  again  into  their  ingredients,  and 
thus  furnish  the  means  of  procuring  pure  oxygen.  Iron 
and  copper,  when  strongly  heated  and  exposed  to  the  air, 
acquire  oxygen,  but  from  the  oxides  of  these  metals 
(forge  cinder,  copper  scale)  it  is  not  possible  to  separate 
pure  oxygen.  If,  however,  the  metal  mercury  (quicksil- 
ver) be  kept  for  a  long  time  near  the  temperature  at 
which  it  boils,  it  is  slowly  converted  into  a  red  powder 
(red  precipitate,  red  oxide  of  mercury,  or  mercuric  ox- 
ide), which  on  being  more  strongly  heated  is  decomposed, 
yielding  metallic  mercury  and  gaseous  oxygen  in  a  pure 
state. 

The  substance  usually  employed  as  the  most  convenient 
source  of  oxygen  gas  is  the  white  salt  called  potassium 
2 


18 


HOW  CHOPS  GROW. 


chlorate.    Exposed  to  heat,  this  body  melts,  and  present* 
ly  evolves  oxygen  in  great  abundance. 

EXP.  4.— The  following  figure  illustrates  the  apparatus  employed  for 
preparing  and  collecting  this  gas. 

A  tube  of  difficultly  fusible  glass,  8  inches  long  and  J  inch  wide,  con- 
tains the  red  oxide  of  mercury  or  potassium  chlorate.*  To  its  mouth  is 
connected,  air-tight,  by  a  cork,  a  narrow  tube,  the  free  extremity  of 
which  passes  under  the  shelf  of  a  tub  nearly  filled  with  water.  The 
shelf  has,  beneath,  a  funnel-shaped  cavity  opening  above  by  a  narrow 
orifice,  over  which  a  bottle  filled  with  water  is  inverted.  Heat  being 


Pig.  2. 


applied  to  the  wide  tube,  the  common  air  it  contains  is  first  expelled, 
and  presently,  oxygen  bubbles  rapidly  into  the  bottle  and  displaces 
the  water.  When  the  bottle  is  full,  it  may  be  corked  and  set  aside,  and 
its  place  supplied  by  another.  Fill  four  pint  bottles  with  the  gas,  and 
set  them  aside  with  their  mouths  in  tumblers  of  water.  From  one 
ounce  of  potassium  chlorate  about  a  gallon  of  oxygen  gas  may  be  thus 
obtained,  which  is  not  quite  pure  at  first,  but  becomes  nearly  so  on 
standing  over  water  for  some  hours.  When  the  escape  of  gas  becomes 
slow  and  cannot  be  quickened  by  increased  heat,  remove  the  delivery- 
tube  from  the  water,  to  prevent  the  latter  receding  and  breaking  the 
apparatus. 

As  this  gas  makes  no  peculiar  impressions  on  the  senses, 


*  The  potassium  chlorate  is  best  mixed  with  about  one-quarter  its 
weight  of  powdered  black  oxide  of  manganese,  as  this  facilitates  the 
preparation,  and  renders  the  heat  of  a  common  alcohol  lamp  sufficient* 


10 

we  employ  its  behavior  toward  other  bodies  for  its  recog- 
nition. 

EXP.  5. — Place  a  burning  splinter  of  wood  In  a  vessel  of  oxygen  (lifted 
for  that  purpose,  mouth  upward,  from  the  water).  The  flame  is  at  once 
greatly  increased  in  brilliancy.  Now  remove  the  splinter  from  the 
bottle,  blow  out  the  flame,  and  thrust  the  still  glowing  point  into  the 
oxygen.  It  is  instantly  relighted.  The  experiment  may  be  repeated 
many  times.  This  is  the  usual  test  for  oxygen  gas. 

Combustion. — When  the  chemical  union  of  two  bodies 
takes  place  with  such  energy  as  to  produce  visible  phe- 
nomena of  fire  or  flame,  the  process  is  called  combustion. 
Bodies  that  burn  are  combustibles,  and  the  gas  in  which 
a  substance  burns  is  called  a  supporter  of  combustion. 

Oxygen  is  the  grand  supporter  of  combustion,  and 
nearly  all  cases  of  burning  met  with  in  ordinary  experi- 
ence are  instances  of  chemical  union  between  the  oxygen 
of  the  atmosphere  and  some  other  body  or  bodies. 

The  rapidity  or  intensity  of  combustion  depends  upon 
the  quantities  of  oxygen  and  of  the  combustible  that 
unite  within  a  given  time.  Forcing  a  stream  of  air  into 
a  fire  increases  the  supply  of  oxygen  and  excites  a  more 
vigorous  combustion,  whether  it  be  done  by  a  bellows  or 
result  from  ordinary  draught. 

Oxygen  exists  in  our  atmosphere  to  the  extent  of  about 
one-fifth  of  the  bulk  of  the  latter.  When  a  burning  body 
is  brought  into  unmixed  oxygen,  its  combustion  is,  of 
course,  more  rapid  than  in  ordinary  air,  four-fifths  of 
which  is  a  gas,  presently  to  be  noticed,  that  is  compara- 
tively indifferent  in  its  chemical  affinities  toward  most 
bodies. 

In  the  air  a  piece  of  burning  charcoal  soon  goes  out ; 
but  if  plunged  into  oxygen,  it  burns  with  great  rapidity 
and  brilliancy. 

EXP.  6.— Attach  a  slender  bit  of  charcoal  to  one  end  of  a  sharpened 
wire  that  is  passed  through  a  wide  cork  or  card ;  heat  the  charcoal  to 
redness  in  the  flame  of  a  lamp,  and  then  insert  it  into  a  bottle  of  oxy- 
gen, Fig.  3.  When  the  combustion  has  declined,  a  suitable  test  applied 


20 


HOW  CEOPS  GROW. 


to  the  air  of  the  bottle  will  demonstrate  that  another  invisible  gas  has 
taken  the  place  of  the  oxygen.  Such  a  test  is  lime-water.* 
On  pouring  some  of  this  into  the  bottle  and  agitating 
vigorously,  the  previously  clear  liquid  becomes  milky, 
and,  on  standing,  a  white  deposit,  or  precipitate,  as  the 
chemist  terms  it,  gathers  at  the  bottom  of  the  vessel. 
Carbon,  by  thus  uniting  to  oxygen,  yields  carbonic  acid 
gas,  which  in  its  turn  combines  with  lime,  producing 
carbonate  of  lime.  These  substances  will  be  further 
noticed  in  a  subsequent  chapter. 

Metallic  iron  is  incombustible  in  the  at- 
mosphere under  ordinary  circumstances,  but 
3'        if  heated  to  redness  and  brought  into  pure 
oxygen  gas,  it  burns  as  readily  as  wood  burns  in  the  air. 

EXP.  7.— Provide  a  thin  knitting-needle,  heat  one  end  red  hot,  and 
sharpen  it  by  means  of  a  file.  Thrust  the  point  thus 
made  into  a  splinter  of  wood  (a  bit  of  the  stick  of  a 
match,  J  inch  long) ;  pass  the  other  end  of  the  needle 
through  a  wide,  flat  cork  for  a  support ;  set  the  wood  on 
fire,  and  immerse  the  needle  in  a  bottle  of  oxygen,  Fig. 
4.  After  the  wood  consumes,  the  iron  itself  takes  fire 
and  burns  with  vivid  scintillations.  It  is  converted  into 
two  distinct  oxides  of  iron,  of  which  one,— ferric  oxide,— 
will  be  found  as  a  yellowish-red  coating  on  the  sides  of 
the  bottle ;  the  other,— magnetic  oxide,— will  fuse  to 
black,  brittle  globules,  which  falling,  often  melt  quite 
into  the  glass.  Fig.  4. 

The  only  essential  difference  between  these  and  ordi- 
nary cases  of  combustion  is  the  intensity  with  which  the 
process  goes  on,  due  to  the  more  rapid  access  of  oxygen 
to  the  combustible. 

Many  bodies  unite  slowly  with  oxygen, — oxidize,  as  it 
is  termed, — without  these  phenomena  of  light  and  intense 
heat  which  accompany  combustion.  Thus  iron  rusts,  lead 
tarnishes,  wood  decays.  All  these  processes  are  cases  of 
oxidation,  and  cannot  go  on  in  the  absence  of  oxygen. 

Since  the  action  of  oxygen  on  wood  and  other  organic 
matters  at  common  temperatures  appears  to  be  analogous 

*  To  prepare  lime-water,  put  a  piece  of  unslaked  lime,  as  large  as  a 
chestnut,  into  a  pint  of  water,  and  after  it  lias  fallen  to  powder,  agitate 
the  whole  for  a  few  minutes  in  a  well-stoppered  bottle.  On  standing, 
the  excess  of  lime  will  settle,  and  the  perfectly  clear  liquid  above  it  is 
ready  for  use. 


THE  VOLATILE  PART  OF  PLANTS.        21 

in  a  chemical  sense  to  actual  burning,  Liebig  has  pro- 
posed the  term  eremacausis  (slow  burning),  to  designate 
the  chemical  process  of  oxidation  which  takes  place  in 
decay,  and  which  is  concerned  in  many  transformations, 
as  in  the  making  of  vinegar  and  the  formation  of  salt- 
peter.* 

Oxygen  is  necessary  to  organic  life.  The  act  of  breath- 
ing introduces  it  into  the  lungs  and  blood  of  animals, 
where  it  aids  the  important  office  of  respiration.  Ani- 
mals, and  plants  as  well,  speedily  perish  if  deprived  of 
free  oxygen,  which  has  therefore  been  called  vital  air. 

Oxygen  has  a  nearly  universal  tendency  to  combine 
with  other  substances,  and  form  with  them  new  com- 
pounds. With  carbon,  as  we  have  seen,  it  forms  carbonic 
acid  gas  or  carbon  dioxide.  With  iron  it  unites  in  vari- 
ous proportions,  giving  origin  to  several  distinct  oxides. 
In  decay,  putrefaction,  fermentation,  and  respiration, 
numberless  new  products  are  formed,  the  results  of  its 
chemical  affinities. 

Oxygen  is  estimated  to  be  the  most  abundant  body  in 
nature.  In  the  free  State,  but  mixed  with  other  gases,  it 
constitutes  one-fifth  of  the  bulk  of  the  atmosphere.  In 
chemical  union  with  other  bodies,  it  forms  eight-ninths 
of  'the  weight  of  all  the  water  of  the  globe,  and  one-third 
of  its  solid  crust, — its  soils  and  rocks, — as  well  as  of  all 
the  plants  and  animals  which  exist  upon  it.  In  fact, 
tli ere  are  but  few  compound  substances  occurring  in  or- 
dinary experience  into  which  oxygen  does  not  enter  as  a 
necessary  ingredient. 

Nitrogen. — This  body  is  the  other  chief  constituent  of 
the  atmosphere,  of  which  it  makes  up  about  four-fifths 
the  bulk,  and  in  which  its  office  would  appear  to  be 

*  Recent  investigation  has  demonstrated  that  the  oxidations  which 
Liebig  classed  under  the  term  eremacausis,  are  for  the  most  part  strict- 
ly dependent  on  the  vital  processes  of  extremely  minute  organisms, 
which  are  in  general  characterized  by  the  terms  microbes  or  micro- 
demes,  and  are  more  specifically  designated  bacteria,  i.  e.,  "rod-shaped 
animalcules  or  plautlets." 


22  fiow  CROPS  GROW. 

mainly  that  of  diluting  and  tempering  the  affinities  of 
oxygen.  Indirectly,  however,  it  serves  other  most  im- 
portant uses,  as  will  presently  be  seen. 

For  the  preparation  of  nitrogen  we  have  only  to  remove 
the  oxygen  from  a  portion  of  atmospheric  air.  This  may 
be  accomplished  more  or  less  perfectly  by  a  variety  of 
methods.  "We  have  just  learned  that  the  process  of  burn- 
ing is  a  chemical  union  of  oxygen  with  the  combustible. 
If,  now,  we  can  find  a  body  which  is  very  combustible 
and  one  which  at  the  same  time  yields  by  union  with  ox- 
ygen a  product  that  may  be  readily  removed  from  the  air 
in  which  it  is  formed,  the  preparation  of  nitrogen  from 
ordinary  air  becomes  easy.  Such  a  body  is  phosphorus, 
a  substance  to  be  noticed  in  some  detail  presently. 

EXP.  8. — The  bottom  of  a  dinner-plate  is  covered  half  an  Inch  deep 
with  water ;  a  bit  of  chalk  hollowed  out  into  a  little  cup  is  floated  on 
the  water  by  means  of  a  large  flat  cork  or  a  piece  of  wood ;  into  this 
cup  a  morsel  of  dry  phosphorus  as  large  as  a  pepper- 
corn is  placed,  which  is  then  set  on  fire  and  covered  by 
a  capacious  glass  bottle  or  bell-jar.  The  phosphorus 
burns  at  first  with  a  vivid  light,  which  is  presently  ob- 
scured by  a  cloud  of  snow-like  phosphoric  acid.  The 
combustion  goes  on,  however,  until  nearly  all  the  oxy- 
gen is  removed  from  the  included  air.  The  air  is  at 
first  expanded  by  the  heat  of  the  flame,  and  a  portion 
of  it  escapes  from  the  vessel ;  afterward  it  diminishes 
in  volume  as  its  oxygen  is  removed,  so  that  it  is  need- 
ful  to  pour  water  on  the  plate  to  prevent  the  external 
air  from  passing  into  the  vessel.  After  some  time  the  white  fume  will 
entirely  fall,  and  be  absorbed  by  the  water,  leaving  the  inclosed  nitro- 
gen quite  clear. 

EXP.  9.— Another  instructive  method  of  preparing  nitrogen  is  the  fol- 
lowing: A  handful  of  green  vitriol  (protosulphate  of  iron  or  ferrous 
sulphate)  is  dissolved  in  half  a  pint  of  water,  the  solution  is  put  into 
a  quart  bottle,  a  gill  of  ammonia-water  or  fresh  potash-lye  is  added, 
the  bottle  stoppered,  and  the  mixture  vigorously  agitated  for  some 
minutes ;  the  stopper  is  then  lifted,  to  allow  fresh  air  to  enter,  and  the 
whole  is  again  agitated  as  before.  This  is  repeated  occasionally  for  half 
an  hour  or  more,  until  no  further  absorption  takes  place,  when  nearly 
pure  nitrogen  remains  in  the  bottle. 

Free  nitrogen,  under  ordinary  circumstances,  mani- 
fests no  active  properties,  but  is  best  characterized  by  its 
chemical  indifference  to  most  other  bodies.  That  it  is 


THE  VOLATILE  PAET  OF  PLANTS.  23 

incapable  of  supporting  combustion  is  proved  by  the  first 
method  we  have  instanced  for  its  preparation. 

EXP.  10. — A  burning  splinter  is  immersed  in  the  bottle  containing  the 
nitrogen  prepared  by  the  second  method,  Exp.  9;  the  flame  immediate- 
ly goes  out. 

Nitrogen  cannot  maintain  respiration,  so  that  animals 
perish  if  confined  in  it.  Vegetation  also  dies  in  an  at- 
mosphere of  this  gas.  For  this  reason  it  was  formerly 
called  .Azote  (against  life).  In  general  it  is  difficult  to 
effect  direct  union  of  nitrogen  with  other  bodies,  but  at 
a  high  temperature,  in  presence  of  alkalies,  it  unites  with 
carbon,  forming  cyanides. 

The  atmosphere  is  the  great  store  and  source  of  nitro- 
gen in  nature.  In  the  mineral  kingdom,  especially  in 
soils,  it  occurs  in  small  relative  proportion,  but  in  large 
aggregate  quantity  as  an  ingredient  of  saltpeter  and  other 
nitrates,  and  of  ammonia.  It  is  a  constant  constituent 
of  all  plants,  and  in  the  animal  it  is  a  never-absent  com- 
ponent of  the  working  tissues,  the  muscles,  tendons  and 
nerves,  and  is  hence  an  indispensable  ingredient  of  food. 

Hydrogen. — Water,  which  is  so  abundant  in  nature, 
and  so  essential  to  organic  existence,  is  a  compound  of 
two  elements,  viz. :  oxygen,  that  has  already  been  consid- 
ered, and  hydrogen,  which  we  now  come  to  notice. 

Hydrogen,  like  oxygen,  is  a  gas,  destitute,  when  pure, 
of  either  odor,  taste,  or  color.  It  does  not  occur  nat- 
urally in  the  free  state,  except  in  small  quantity  in  the 
emanations  from  boiling  springs  and  volcanoes.  Its  most 
simple  preparation  consists  in  abstracting  oxygen  from 
water  by  means  of  agents  which  have  no  special  affinity 
for  hydrogen,  and  therefore  leave  it  uncombined. 

Sodium,  a  metal  familiar  to  the  chemist,  has  such  an 
attraction  for  oxygen  that  it  decomposes  water  with  great 
rapidity. 

Exp.  11. — Hydrogen  is  therefore  readily  procured  by  inverting  a  bot- 
tle full  of  water  in  a  bowl,  and  inserting  into  it  a  bit  of  sodium  as  large 
*s  a  pea.  The  sodium  should  first  be  wiped  tree  from  the  naphtha  in 


24  HOW  CROPS  GROW. 

which  it  is  kept,  and  then  be  wrapped  tightly  in  several  folds  of  paper. 
On  bringing  it,  thus  prepared,  under  the  mouth  of  the  bottle,  it  floats 
upward,  and  when  the  water  penetrates  the  paper,  an  abundant  escape 
of  gas  occurs. 

Metallic  iron,  when  at  a  red  heat,  rapidly  decomposes 
water,  uniting  with  oxygen  and  setting  hydrogen  free, 
as  may  be  shown  by  passing  steam  from  boiling  water 
through  a  gun-barrel  filled  with  iron-turnings  and  heated 
to  bright  redness.  Certain  acids  which  contain  hydro- 
gen are  decomposed  by  iron,  zinc,  and  some  other  metals, 
their  hydrogen  being  separated  as  gas,  while  the  metal 
takes  the  place  of  the  hydrogen  with  formation  of  a  salt. 
Hydrochloric  acid  (formerly  called  muriatic  acid)  is  a 
compound  of  hydrogen  with  chlorine,  and  may  accord- 
ingly be  termed  hydrogen  chloride.  When  this  acid  is 
poured  upon  zinc  the  latter  takes  the  chlorine,  forming 
zinc  chloride,  and  hydrogen  escapes  as  gas.  Chemists 
represent  such  changes  by  the  use  of  symbols  (first  letters 
of  the  names  of  chemical  elements),  as  follows  : 

H.  1^1    i    rrn  VT»  ^-'1     I     •**•  *-vi» 

HC1  +  Zn_Zncl  +  Hor 

2  (H  Cl)  -\-  Zn  =  Zn  C12  +  H, 

EXP.  12.— Into  a  bottle  fitted  with  cork,  funnel,  and  delivery  tubes  (Fig. 
6)  an  ounce  of  iron  tacks  or  zinc 
clippings  is  introduced,  a  gill 
of  water  is  poured  upon  them, 
and  lastly  an  ounce  of  hydro- 
chloric acid  is  added.  A  brisk 
effervescence  shortly  com- 
mences, owing  to  the  escape 
of  nearly  pure  hydrogen  gas, 
which  may  be  collected  in  a 
bottle  filled  with  water  as  di- 
rected for  oxygen.  The  first 
portions  that  pass  over  are 
mixed  with  air,  and  should  be 
rejected,  as  the  mixture  Is  dan- 
gerously explosive. 

One  of  the  most  strik- 
ing properties  of  free  hy-  Fig.  6. 
flrogen  is  its  levity.    It  is  the  lightest  body  in  nature 


THE  VOLATILE  PART  OF  PLANTS. 


fhat  has  been  weighed,  being  fourteen  and  a  half  times 
lighter  than  common  air.  It  is  hence 
)used  in  filling  balloons.  Another  property 
is  its  combustibility ;  it  inflames  on  contact 
with  a  lighted  taper,  and  burns  with  a 
flame  that  is  intensely  hot,  though  scarcely 
luminous  if  the  gas  be  pure.  Finally,  it 
is  itself  incapable  of  supporting  the  com- 
bustion  of  a  taper. 

Exp.  13. — All  these  characters  may  be  shown  by  the  following  single 
experiment.  A  bottle  full  of  hydrogen  is  lifted  from  the  water  over 
which  it  has  been  collected,  and  a  taper  attached  to  a  bent  wire,  Fig.  7, 
is  brought  to  its  mouth.  At  first  a  slight  explosion  is  heard  from  the 
sudden  burning  of  a  mixture  of  the  gas  with  air  that  forms  at  the  mouth 
of  the  vessel ;  then  the  gas  is  seen  burning  on  its  lower  surface  with  a 
pale  flame.  If  now  the  taper  be  passed  into  the  bottle  it  will  be  extin- 
guished; on  lowering  it  again,  it  will  be  relighted  by  the  burning  gas; 
finally,  if  the  bottle  be  suddenly  turned  mouth  upwards,  the  light  hy« 
drogen  rises  in  a  sheet  of  flame. 

In  the  above  experiment,  the  hydrogen  burns  only 
where  it  is  in  contact  with  atmospheric  oxygen ;  the  pro- 
duct of  the  combustion  is  an  oxide  of  hydrogen,  the  uni- 
versally diffused  compound,  water.  The  conditions  of 
the  last  experiment  do  not  permit  the  collection  or  iden- 
tification of  this  water ;  its  production  can,  however, 
readily  be  demonstrated. 

EXP.  14.— The  arrangement  shown  in  Fig.  8  may  be  employed  to  exhibit 


Fig.  a 

the  formation  of  water  by  the  burning  of  hydrogen.    Hydrogen  gas  is 
generated  from  zinc  and  dilute  acid  in  the  two-necked  bottle.    Thus 


26  HOW  CHOPS  GEOW. 

produced,  it  is  mingled  with  spray,  to  remove  which  it  is  made  to 
stream  through  a  tube  loosely  filled  with  cotton.  After  air  has  been 
entirely  displaced  from  the  apparatus,  the  gas  is  ignited  at  the  up- 
curved  end  of  the  narrow  tube,  and  a  clean  bell-glass  is  supported  over 
the  flame.  Water  collects  at  once,  as  dew,  on  the  interior  of  the  bell, 
and  shortly  flows  down  in  drops  into  a  vessel  placed  beneath. 

In  the  mineral  world  we  scarcely  find  hydrogen  occur- 
ring in  much  quantity,  save  as  water.  It  is  a  constant 
ingredient  of  plants  and  animals,  and  of  nearly  all  the 
numberless  substances  which  are  products  of  organic  life. 

Hydrogen  forms  with  carbon  a  large  number  of  com- 
pounds, the  most  common  of  which  are  the  volatile  oils, 
like  oil  of  turpentine,  oil  of  lemon,  etc.  The  chief  illu- 
minating ingredient  of  coal  gas  (ethylene  or  olefiant  gas), 
the  coal  or  rock  oils  (kerosene),  together  with  benzine 
and  paraffine,  are  so-called  hydro-carbons. 

Sulphur  is  a  well-known  solid  substance,  occurring  in 
commerce  either  in  sticks  (brimstone,  roll  sulphur)  or  as 
a  fine  powder  (flowers  of  sulphur),  having  a  pale  yellow 
color,  and  a  peculiar  odor  and  taste. 

Uncombined  sulphur  is  comparatively  rare,  the  com- 
mercial supplies  being  almost  exclusively  of  volcanic  ori- 
gin ;  but,  in  one  or  other  form  of  combination,  this  ele- 
ment is  universally  diffused. 

Sulphur  is  combustible.  It  burns  in  the  air  with  a 
pale  blue  flame,  in  oxygem  gas  with  a  beautiful  purple- 
blue  flame,  yielding  in  both  cases  a  suffocating  and  fum- 
ing gas  of  peculiar  nauseous  taste,  which  is  called  sul- 
phurous acid  gas  or  sulphur  dioxide. 

EXP.  15.— Heat  a  bit  of  sulphur  as  large  as  a  grain  of  wheat  on  a  slip 
of  iron  or  glass,  over  the  flame  of  a  spirit  lamp,  for  observing  its  fusion, 
combustion,  and  the  development  of  sulphur  dioxide.  Further,  scoop 
out  a  little  hollow  in  a  piece  of  chalk,  twist  a  wire  round  the  latter  to 
serve  for  a  handle,  as  in  Fig.  3 ;  heat  the  chalk  with  a  fragment  of  sul- 
phur upon  it  until  the  latter  ignites,  and  bring  it  into  a  bottle  of  oxygen 
gas.  The  purple  flame  is  shortly  obscured  by  an  opaque  white  fume  of 
sulphur  dioxide. 

Sulphur  forms  with  oxygen  another  compound,  the  tri- 
oxide,  which,  in  combination  with  water,  constitutes  com- 


THE  VOLATILE  PAET  OF  PLANTS.  27 

mon  sulphuric  acid,  or  oil  of  vitriol.  This  oxide  is  devel- 
oped to  a  slight  extent  during  the  combustion  of  sulphur 
in  the  air  and  the  acid  is  prepared  on  a  large  scale  for 
commerce  by  a  complicated  process. 

Sulphur  unites  with  most  of  the  metals,  yielding  com- 
pounds known  as  sulphides,  or  formerly  as  sulphurets. 
These  exist  in  nature  in  large  quantities,  especially  the 
sulphides  of  iron,  copper,  and  lead,  and  many  of  them 
are  valuable  ores.  Sulphides  may  be  formed  artificially 
by  heating  most  of  the  metals  with  sulphur. 

EXP.  16.— Heat  the  bowl  of  a  tobacco-pipe  to  a  low  red  heat  In  a  stove 
or  furnace ;  have  in  readiness  a  thin  iron  wire  or  watch-spring  made 
into  a  spiral  coil ;  throw  into  the  pipe-bowl  some  lumps  of  sulphur,  and 
when  these  melt  and  boil,  with  formation  of  a  red  vapor  or  gas,  intro- 
duce the  iron  coil,  previously  heated  to  redness,  into  the  sulphur  vapor. 
The  sulphur  and  iron  unite ;  the  iron,  in  fact,  burns  in  the  sulphur  gas, 
giving  rise  to  a  black  iron  sulphide,  in  the  same  manner  as  in  Exp.  7  it 
burned  in  oxygen  gas  and  produced  an  iron  oxide.  The  iron  sulphide 
melts  to  brittle,  round  globules,  and  remains  in  the  pipe-bowl. 

With  hydrogen,  the  element  we  are  now  considering 
unites  to  form  a  gas  that  possesses  in  a  high  degree  the 
odor  of  rotten  eggs,  and  is,  in  fact,  the  chief  cause  of  the 
noisomeness  of  this  kind  of  putridity.  This  gas,  com- 
monly called  sulphuretted  hydrogen,  or  hydrogen  sulphide, 
is  dissolved  in,  and  evolved  abundantly  from,  the  water 
of  sulphur  springs.  It  may  be  produced  artificially  by 
acting  on  some  metallic  sulphides  with  dilute  sulphuric 
or  hydrochloric  acid. 

EXP.  17.— Place  a  lump  of  the  iron  sulphide  prepared  in  Exp.  16  in  a  cup 
or  wine-glass,  add  a  little  water,  and  lastly  a  little  hydrochloric  acid. 
Bubbles  of  hydrogen  sulphide  will  shortly  escape. 

In  soils,  sulphur  occurs  almost  invariably  in  the  form 
of  sulphates,  compounds  of  sulphuric  acid  with  metals,  a 
class  of  bodies  to  be  hereafter  noticed. 

In  plants,  sulphur  is  always  present,  though  usually  in 
small  proportion.  The  turnip,  the  onion,  mustard,  horse- 
radish, and  assafoatida  owe  their  peculiar  flavors  to  vola- 
tile oils  of  which  sulphur  is  an  ingredient. 


28  HOW  CROPS  GROW. 

Albumin,  globulin,  casein  and  similar  principles,  never 
absent  from  plant  or  animal,  possess  also  a  small  con- 
tent of  sulphur.  In  hair  and  horn  it  occurs  to  the  amount 
of  three  to  five  per  cent. 

When  organic  matters  are  burned  with  full  access  of 
air,  their  sulphur  is  oxidized  and  remains  in  the  ash  as 
sulphates,  or  escapes  into  the  air  as  sulphur  dioxide. 

Phosphorus  is  an  element  which  has  such  intense  af- 
finities for  oxygen  that  it  never  occurs  naturally  in  the 
free  state,  and  when  prepared  by  art,  is  usually  obliged  to 
be  kept  immersed  in  water  to  prevent  its  oxidizing,  or 
even  taking  fire.  It  is  known  to  the  chemist  in  the  solid 
state  in  two  distinct  forms.  In  the  more  commonly  oc- 
curring form,  it  is  colorless  or  yellow,  translucent,  wax- 
like  in  appearance ;  is  intensely  poisonous,  inflames  by 
moderate  friction,  and  is  luminous  in  the  dark ;  hence  its 
name,  derived  from  two  Greek  words  signifying  light- 
bearer.  The  other  form  is  brick-red,  opaque,  far  less  in- 
flammable, and  destitute  of  poisonous  properties.  Phos- 
phorus is  extensively  employed  for  the  manufacture  of 
friction  matches.  For  this  purpose  yellow  phosphorus  is 
chiefly  used.  When  burned  in  air  or  in  oxygen  gas  this  ele- 
ment forms  a  white  substance — phosphorus  pentoxide 
(formerly  termed  anhydrous  phosphoric  acid) — which  dis- 
solves in  water,  at  the  same  time  uniting  chemically  with 
a  portion  of  the  latter,  and  thus  yielding  a  body  of  the 
utmost  agricultural  importance,  viz.,  phosphoric  acid, 

EXP.  18. — Burn  a  bit  of  phosphorus  under  a  bottle,  as  in  Exp.  8,  omit- 
ting the  water  on  the  plate.  The  snow-like  cloud  of  phosphorus  pen- 
toxide gathers  partly  on  the  sides  of  the  bottle,  but  mostly  on  the  plate. 
It  attracts  moisture  when  exposed  to  the  air,  and  hisses  from  develop- 
ment of  heat  when  put  into  water.  Dissolve  a  portion  of  it  in  hot 
water,  and  observe  that  the  solution  is  acid  to  the  taste.  Finally  evapo- 
rate the  solution  to  dryness  at  a  gentle  heat.  Instead  of  recovering 
thus  the  white  opaque  phosphorus  pentoxide,  the  residue  is  a  trans- 
parent mass  of  phosphoric  acid,  a  compound  of  phosphorus,  oxygen 
and  hydrogen. 

In  nature  phosphorus  is  usually  found  in  the  form  of 


THE  VOLATILE   PART  OF  PLANTS.  29 

phosphates,  which  are  phosphoric  acid  whose  hydrogen 
has  been  partly  or  entirely  replaced  by  metals. 

In  plants  and  animals,  it  exists  for  the  most  part  as 
phosphates  of  calcium  (or  lime),  magnesium  (or  mag- 
nesia), potassium  (or  potash),  and  sodium  (or  soda). 

The  bones  of  animals  contain  a  considerable  proportion 
(10  per  cent.)  of  phosphorus,  mainly  in  the  form  of  cal- 
cium phosphate.  It  is  from  this  that  the  phosphorus 
employed  for  matches  is  largely  procured. 

EXP.  19.— Burn  a  piece  of  bone  in  a  fire  until  it  becomes  white,  or 
nearly  so.  The  bone  loses  about  half  its  weight.  What  remains  is 
bone-earth  or  bone-ash,  and  of  this  90  per  cent,  is  calcium  phosphate. 

Phosphates  are  readily  formed  by  bringing  together 
solutions  of  various  metals  with  solution  of  phosphoric 
acid. 

EXP.  20. — Pour  into  each  of  two  wine  or  test  glasses  a  small  quantity 
of  the  solution  of  phosphoric  acid  obtained  in  Exp.  18.  To  one,  add 
some  lime-water  (see  note  p.  19)  until  a  white  cloud  or  precipitate  is  per- 
ceived. This  is  a  calcium  phosphate.  Into  the  other  portion  drop  solu- 
tion of  alum.  A  translucent  cloud  of  aluminium  phosphate  is  immedi- 
ately produced. 

In  soils  and  rocks,  phosphorus  exists  in  the  state  of 
phosphates  of  calcium,  aluminium,  and  iron. 

The  tissues  and  juices  of  animals  and  plants  generally 
contain  small  proportions  of  several  highly  complex  "  or- 
ganic compounds"  in  which  phosphoric  acid  is  associated 
with  the  elements  carbon,  oxygen,  hydrogen  and  nitrogen. 
Such  substances  are  chlorophyll,  lecithin  and  nuclein, 
to  be  noticed  hereafter. 

We  have  thus  briefly  considered  the  more  important 
characters  of  those  six  bodies  which  constitute  that  part 
of  plants,  and  of  animals  also,  which  is  volatile  or  de- 
structible at  high  temperatures,  viz. :  carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur,  and  phosphorus. 

Out  of  these  substances,  which  are  often  termed  the 
organic  elements  of  vegetation,  are  chiefly  compounded  all 
the  numberless  products  of  life  to  be  met  with,  either  in 
the  vegetable  or  animal  world. 


30  HOW  CROPS  GROW. 

ULTIMATE  COMPOSITION   OF  VEGETABLE  MATTER. 

To  convey  an  idea  of  the  relative  proportions  in  which 
these  six  elements  exist  in  plants,  a  statement  of  the 
ultimate  or  elementary  percentage  composition  of  several 
kinds  of  vegetable  matter  is  here  subjoined. 

Grain  of  Straw  of  Tubers  of  Grain  of  Hay  of  Red, 

Wheat.  Wheat.  Potato.  Peas.  Clover. 

Carbon  ......................    46.1  48.4  44.0  46.5  47.4 

Hydrogen  ...................      5.8  5.3  5.8  6.2  5.0 

Oxygen  ......................    43.4  38.9  44.7  40.0  37.8 

Nitrogen  ....................      2.3  0.4  1.5  4.2  2.1 

Ash,     including    sulphur   \9.  7ft  4n  ,1  7T 
and  phosphorus 

100.0  100.0  100.0  100.0  100.0 

3ulj5hur  ...................    0.12  0.14  0.08  0.21  0.18 

Phosphorus  .................    0.30  0.80  0.34  0.34  0.20 

Our  attention  may  now  be  directed  to  the  study  of  such 
compounds  of  these  elements  as  constitute  the  basis  of 
plants  in  general  ;  since  a  knowledge  of  them  will  pre- 
pare us  to  consider  the  remaining  elements  with  a  greater 
degree  of  interest. 

Previous  to  this,  however,  we  must,  first  of  all,  gain  a 
clear  idea  of  that  force  —  chemical  affinity  —  in  virtue  of 
whose  action  these  elements  are  held  in  their  combina- 
tions and,  in  order  to  understand  the  language  of  chem- 
ical science,  must  know  something  of  the  views  that  now 
prevail  as  to  the  constitution  of  matter. 


CHEMICAL  AFFINITY.  —  THE  ATOMIC-MOLECULAR  THEORY. 

Chemical  Attraction  or  Affinity  is  that  force  or 
kind  of  energy  which  unites  or  combines  two  or  more  sub- 
stances of  unlike  character,  to  a  new  body  different  from 
its  ingredients. 

Chemical  Combination  differs  essentially  from  mere 
mixture.  Thus  we  may  put  together  in  a  vessel  the  two 
gases,  oxygen  and  hydrogen,  and  they  will  remain  uncom- 
biued  for  an  indefinite  time,  occupying  their  original  vol- 


THE  VOLATILE  PAET  OP  PLANTS.  31 

time  ;  but  if  a  flame  be  brought  into  the  mixture  they  in- 
stantly unite  with  a  loud  explosion,  and,  in  place  of  the 
light  and  bulky  gases,  we  find  a  few  drops  of  water,  which 
is  a  liquid  at  ordinary  temperatures,  and  in  winter 
weather  becomes  solid,  which  does  not  sustain  combus- 
tion like  oxygen,  nor  itself  burn  as  does  hydrogen ;  but 
is  a  substance  having  its  own  peculiar  properties,  differ- 
ing from  those  of  all  other  bodies  with  which  we  are  ac- 
quainted. 

In  the  atmosphere  we  have  oxygen  and  nitrogen  in  a 
state  of  mere  mixture,  each  of  these  gases  exhibiting  its 
own  characteristic  properties.  When  brought  into  chem- 
ical combination,  they  are  capable  of  yielding  a  series  of 
no  less  than  five  distinct  compounds,  one  of  which  is  the 
so-called  laughing-gas,  while  the  others  form  suffocating 
and  corrosive  vapors  that  are  totally  irrespirable. 

Chemical  Decomposition. — Water,  thus  composed 
or  put  together  by  the  exercise  of  affinity,  is  easily  de- 
composed or  taken  to  pieces,  so  to  speak,  by  forces  that 
oppose  affinity — e.  g.,  heat  and  electricity — or  by  the 
greater  affinity  of  some  other  body — e.  g.,  sodium — as  al- 
ready illustrated  in  the  preparation  of  hydrogen,  Exp.  11. 

Definite  Proportions. — A  further  distinction  be- 
tween chemical  union  and  mere  mixture  is,  that,  while 
two  or  more  bodies  may,  in  general,  be  mixed  in  all  pro- 
portions, bodies  combine  chemically  in  comparatively 
few  proportions  which  are  fixed  and  invariable.  Oxygen 
and  hydrogen,  e.  g.,  are  found  united  in  nature,  princi- 
pally in  the  form  of  water  ;  and  water,  if  pure,  is  always 
composed  of  one-ninth  hydrogen  and  eight-ninths  oxy- 
gen by  weight,  or,  since  oxygen  is,  bulk  for  bulk,  sixteen 
times  heavier  than  hydrogen,  of  one  volume  or  measure 
of  oxygen  to  two  volumes  of  hydrogen. 

Atoms. — It  is  now  believed  that  matter  of  all  kinds 
consists  of  indivisible  and  unchangeable  particles  called 
atoms,  which  are  united  to  each  other  by  chemical  at- 


32  HOW  CEOPS  GROW. 

traction,  and  cannot  ordinarily  exist  in  the  free  state. 
On  this  view  each  particular  kind  of  matter  or  chemical 
substance  owes  its  individuality  either  to  the  special  kinds 
or  to  the  numbers  of  the  atoms  it  consists  of.  Atoms 
may  be  defined  as  the  smallest  quantities  of  matter  which 
can  exist  in  chemical  combination  and  the  smallest  of 
which  we  have  any  knowledge  or  conception. 

Atomic  Weight  of  Elements. — On  the  hypothesis 
that  chemical  union  takes  place  between  atoms  of  the 
elements,  the  simplest  numbers  expressing  the  propor- 
tions by  weight*  in  which  the  elements  combine,  are  ap- 
propriately termed  atomic  weights.  These  numbers  are 
only  relative,  and  since  hydrogen  is  the  element  which 
unites  in  the  smallest  proportion  by  weight,  it  is  assumed 
as  the  standard  unit.  From  the  results  of  a  great 
number  of  the  most  exact  experiments,  chemists  have 
generally  agreed  upon  the  atomic  weights  given  in  the 
subjoined  table  for  the  elements  already  mentioned  or 
described. 

Symbols. — For  convenience  in  representing  chemical 
changes,  the  first  letter  (or  letters)  of  the  Latin  name 
of  the  element  is  employed  instead  of  the  name  itself,  and 
is  termed  its  symbol. 

TABLE  OP  ATOMIC  WEIGHTS  AND  SYMBOLS  OF  ELEMENTS.f 


Element.             Atomic  Weight. 

Symbol. 

Hydrogen 

1 

H 

Carbon 

12 

C 

Oxygen 

16 

O 

Nitrogen 

14 

N 

Sulphur 

32 

S 

Phosphorus 

31 

P 

Chlorine 

35.5 

Cl 

Mercury 

200 

Hg  (Hydrargyrum) 

Potassium 

39 

K   (Kalium) 

Sodium 

23 

Na  (Natrium) 

Calcium 

40 

Ca 

Iron 

56 

Fe  (Ferrum) 

*  Unless  otherwise  stated,  parts  or  proportions  by  weight  are  always 
to  be  understood. 

t  Now,  chemists  receive  as  the  true  atomic  weights  double  the  num- 
bers "that  were  formerly  employed,  those  of  hydrogen,  chlorine  and  a 
few  others  excepted.  "The  atomic  weights  here  given  are  mostly  whole 
numbers.  The  actual  atomic  weights,  as  experimentally  determined, 
differ  from  the  above  by  small  fractions,  wluch  may  be  neglected. 


THE  VOLATILE  PART  OF  PLANTS.  33 

Multiple  Proportions. — When  two  or  more  bodies 
unite  in  several  proportions,  their  quantities,  when  not 
expressed  by  the  atomic  weights,  are  twice,  thrice,  four, 
or  more  times,  these  weights ;  they  are  multiples  of  the 
atomic  weights  by  some  simple  number.  Thus,  carbon 
and  oxygen  form  two  commonly  occurring  compounds, 
viz.,  carbon  monoxide,  consisting  of  one  atom  of  each  in- 
gredient, and  carbon  dioxide,  which  contains  to  one  atom, 
or  12  parts  by  weight,  of  carbon,  two  atoms,  or  32  parts 
by  weight,  of  oxygen. 

Molecules*  contain  and  consist  of  chemically-united 
atoms,  and  are  the  smallest  particles  of  matter  that  can 
have  an  individual  or  physical  existence.  While  the 
atoms  compose  and  give  character  to  the  molecules,  the 
molecules  alone  are  sensibly  known  to  us,  and  they  give 
character  to  matter  as  we  find  it  in  masses,  either  solid, 
liquid  or  gaseous.  In  solids  the  molecules  more  or  less 
firmly  cohere  together ;  in  liquids  they  have  but  little 
cohesion,  and  in  gases  they  are  far  apart  and  tend  to  sepa- 
rate from  each  other.  The  so-called  "elements"  are,  in 
fact,  mostly  compounds  whose  molecules  consist  of  two 
or  more  like  atoms,  while  all  other  chemical  substances 
are  compounds  whose  molecules  are  made  up  of  two  or 
more  unlike  atoms. 

Molecular  Weights  of  Compounds. — The  mole- 
cular weight  of  a  compound  is  the  sum  of  the  weights  of 
the  atoms  that  compose  it.  For  example,  water  being 
composed  of  1  atom,  or  16  parts  by  weight,  of  oxygen, 
and  2  atoms,  or  2  parts  by  weight,  of  hydrogen,  has  the 
molecular  weight  of  18.  f 

The  following  scheme  illustrates  the  molecular  compo- 
sition of  a  somewhat  complex  compound,  one  of  the  car- 

*  Latin  diminutive,  signifying  a  little  mass. 

t  We  must  refer  to  recent  treatises  on  chemistry  for  fuller  informa- 
tion as  to  atoms  and  molecules  and  the  methods  of  finding  the  atomic 
and  molecular  weights. 

3 


34  HOW  CEOPS  GBOW. 

bonates  of  ammonium,  which  consists  of  four  elements, 
ten  atoms,  and  has  a  molecular  weight  of  seventy-nine. 

Ammonia  gas  results  from  the  union  of  an  atom  of 
nitrogen  with  three  atoms  of  hydrogen.  One  molecule 
of  ammonia  gas  unites  with  a  molecule  of  carbon  dioxide 
gas  and  a  molecule  of  water  to  produce  a  molecule  of 
ammonium  carbonate. 

Atoms.  Atomic  Molecular 
weights,  weights. 

{Ammonia          (Hydrogen,     3      =      3  )   _117"| 
Imol.  —{Nitrogen,       1      =    14  {  —  *' 
Carbon  di-         ( Carbon,          1      =    12  )   -44  I  _79 
oxide  1  mol.- }  Oxygen,          2       =    32  }   ~ 
Water,  _<  Hydrogen,     2      =      2  )   _la 

1  mol.— \  Oxygen,         1      =:    16  j  — 18J 

Notation  and  Formulas  of  Compounds. — For  the 
purpose  of  expressing  easily  and  concisely  the  composi- 
tion of  compounds,  and  the  chemical  changes  they 
undergo,  chemists  have  agreed  to  make  the  symbol  of  an 
element  signify  one  atom  of  that  element. 

Thus  H  implies  not  only  the  light,  combustible  gas 
hydrogen,  but  also  one  part  of  it  by  weight  as  compared 
with  other  elements,  and  S  suggests,  in  addition  to  the 
idea  of  the  body  sulphur,  the  idea  of  32  parts  of  it  by 
weight.  Through  this  association  of  the  atomic  weight 
with  the  symbol,  the  composition  of  compounds  is 
expressed  in  the  simplest  manner  by  writing  the  symbols 
of  their  elements  one  after  the  other.  Thus,  carbon 
monoxide  is  represented  by  CO,  mercuric  oxide  by  HgO, 
and  iron  monosulphide  by  FeS.  The  symbol  00  con- 
veys to  the  chemist  not  only  the  fact  of  the  existence 
of  carbon  monoxide,  but  also  instructs  him  that  its  mole- 
cule contains  an  atom  each  of  carbon  and  of  oxygen,  and 
from  his  knowledge  of  the  atomic  weights  he  gathers  the 
proportions  by  weight  of  the  carbon  and  oxygen  in  it. 

When  a  compound  contains  more  than  one  atom  of  an 
element,  this  is  shown  by  appending  a  small  figure  to  the 
symbol  of  the  latter.  For  example  :  water  consists  of 
two  atoms  of  hydrogen  united  to  one  of  oxygen,  and  iu 


35 


symbol  is  H20.  In  like  manner  the  symbol  of  carbon 
dioxide  is  C02. 

When  it  is  wished  to  indicate  that  more  than  one  mole- 
cule of  a  compound  exists  in  combination  or  is  concerned 
in  a  chemical  change,  this  is  done  by  prefixing  a  large 
figure  to  the  symbol  of  the  compound.  For  instance, 
two  molecules  of  water  are  expressed  by  2  H20. 

The  symbol  of  a  compound  is  usually  termed  a  formula 
and  if  correct  is  a  molecular  formula  and  shows  the  com- 
position of  one  molecule  of  the  substance.  Subjoined  is 
a  table  of  the  molecular  formulas  of  some  of  the  com- 
pounds that  have  been  already  described  or  employed. 

FORMULAS   OF  COMPOUNDS. 

Name.  Formula.     Molecular  Weight. 

Water  HZO  18 

Hydrogen  Sulphide  H2S  34 

Iron  Monosulphide  FeS  88 

Mercuric  Oxide  HgO  216 

Carbon  Dioxide  CO,  44 

Calcium  Chloride  CaCl,  111 

Sulphur  Dioxide  SO,  64 

Sulphur  Trioxide  SO,  80 

Phosphorus  Pentoxide  P2O6  142 

Empirical  and  Rational  Formulas. — It  is  obvious 
that  many  different  formulas  can  be  made  for  a  body  of 
complex  character.  Thus,  the  carbonate  of  ammonium, 
whose  composition  has  already  been  stated  (p.  33),  and 
which  contains 

1  atom  of  Nitrogen, 
1  atom  of  Carbon, 
3  atoms  of  Oxygen,  and 
5  atoms  of  Hydrogen, 

may  be  most  compactly  expressed  by  the  symbol 

NC08H6. 

Such  a  formula  merely  informs  us  what  elements  and 
how  many  atoms  of  each  element  enter  into  the  compo- 
sition of  the  substance.  It  is  an  empirical  formula, 
being  the  simplest  expression  of  the  facts  obtained  by 
analysis  of  the  substance. 

Rational  formulas,  on  the  other  hand,  are  intended  to 
convey  some  notion  as  to  the  constitution,  formation,  or 


HOW  CBOPS  GROW. 


modes  of  decomposition  of  the  body.  For  example,  the 
real  arrangement  of  the  atoms  in  ammonium  carbonate 
is  believed  to  be  expressed  by  the  rational  (or  structural) 
formula 


=\O-H 

in  which  the  carbon  is  directly  united  to  oxygen,  to 
which  latter  one  hydrogen  and  the  nitrogen  are  also 
linked,  the  remaining  hydrogens  being  combined  to  the 
nitrogen. 

Valence.  —  The  connecting  lines  or  dashes  in  the  fore- 
going formula  show  the  valence  of  the  several  atoms,  i.  e.  , 
their  "atom-fixing  power."  The  single  dash  from  H 
indicates  that  hydrogen  is  univalent  or  lias  a  valence  of 
one.  The  two  dashes  connected  with  0  express  the 
bivalence  of  oxygen  or  that  the  atom  of  this  element  can 
combine  with  two  hydrogens  or  other  univalent  atoms. 
The  nitrogen  is  united  on  one  hand  with  4  hydrogen 
atoms,  and  also,  on  the  other  hand,  satisfies  half  the  val- 
ence of  oxygen  ;  it  is  accordingly  quinquivalent,  i.  e.  ,  has 
five  units  of  valence.  Carbon  is  quadrivalent,  being 
joined  to  oxygen  by  four  units  of  valence. 

Equations  of  Formulas  serve  to  explain  the  results 
of  chemical  reactions  and  changes.  Thus,  the  breaking 
up  by  heat  of  potassium  chlorate  into  potassium  chloride 
and  oxygen  is  expressed  by  the  following  statement: 

Potassium  Chlorate.  Potassium  Chloride.  Oxygen 

2  KC1O,  =  2  KC1  +  3  O, 

The  sign  of  equality,  =,  shows  that  what  is  written 
before  it  supplies  and  is  resolved  into  what  follows  it. 
The  sign  -j-  indicates  and  distinguishes  separate  com- 
pounds. 

The  employment  of  this  kind  of  short-hand  for  exhib- 
iting chemical  changes  will  find  frequent  illustration  as 
we  proceed  with  onr  subject. 

Modes    of    Stating   Composition   of   Chemical 


$7 

Compounds. — These  are  two:  1,  atomic  or  molecular 
statements,  and  2,  centesimal  statements,  or  proportions 
in  one  hundred  parts  (per  cent,  p.  c.,  or  %).  These 
modes  of  expressing  composition  are  very  useful  for  com- 
paring together  different  compounds  of  the  same  ele- 
ments, and,  while  usually  the  atomic  statement  answers 
for  substances  which  are  comparatively  simple  in  their 
composition,  the  statement  per  cent  is  more  useful  for 
complex  bodies.  The  composition  of  the  two  compounds 
of  carbon  with  oxygen  is  given  below  according  to  both 
methods. 

Atomic.  Per  cent.  Atomic.  Percent. 

Carbon  (C),  12         42.86  (C)  12  27.27 

Oxygen  (O),  16         57.14  (O2)  32  72.73 

Carbon  Monoxide  (CO),   28       100.00  Carbon  Dioxide  (CO2),  44         100.00 

The  conversion  of  one  mode  of  statement  into  the  other  is  a  case  of 
simple  rule  of  three,  which  is  illustrated  in  the  following  calculation 
of  the  centesimal  composition  of  water  from  its  molecular  formula. 

Water,  H2O,  has  the  molecular  weight  18,  I.  e.,  it  consists  of  two 
atoms  of  hydrogen,  or  two  parts,  and  one  atom  of  oxygen,  or  sixteen 
parts  by  weight. 

The  arithmetical  proportions  subjoined  serve  for  the  calculation,  viz. : 

H2O         Water  H  Hydrogen 

18  J    100  :  t      2  ;       per  cent  sought  (—11.11) 

H2O         Water  O  Oxygen 

18  '     100  : :       16  :        per  cent  sought  (=88.89) 

By  multiplying  together  the  second  and  third  terms  of  these  propor- 
tions, and  dividing  by  the  first,  we  obtain  the  required  per  cent,  viz.,  of 
hydrogen,  11.11 ;  and  of  oxygen,  88.89. 

The  reader  must  bear  well  in  mind  that  chemical  affin- 
ity manifests  itself  with  very  different  degrees  of  inten- 
sity between  different  bodies,  and  is  variously  modified, 
excited,  or  annulled,  by  other  natural  agencies  and  forces, 
especially  by  heat,  light  and  electricity. 

8  4. 

VEGETABLE     ORGANIC     COMPOUNDS,  OB    PROXIMATE 
PRINCIPLES. 

We  are  now  prepared  to  enter  upon  the  study  of  the 
organic  compounds,  which  constitute  the  vegetable  struc- 


38  HOW  CBOPS  GROW. 

ture,  and  which  are  produced  from  the  elements  carbon, 
oxygen,  hydrogen,  nitrogen,  sulphur,  and  phosphorus,  by 
chemical  agency.  The  number  of  distinct  substances 
found  in  plants  is  practically  unlimited'.  There  are 
already  well  known  to  chemists  hundreds  of  oils,  acids, 
bitter  principles,  resins,  coloring  matters,  etc.  Almost 
every  plant  contains  some  organic  body  peculiar  to  itself, 
and  usually  the  same  plant  in  its  different  parts  reveals 
to  the  senses  of  taste  and  smell  the  presence  of  several 
individual  substances.  In  tea  and  coffee  occurs  an 
intensely  bitter  "  active  principle,"  caffeine.  From 
tobacco  an  oily  liquid  of  eminently  narcotic  and  poison- 
ous properties,  nicotine,  can  be  extracted.  In  the  orange 
are  found  no  less  than  three  oils  ;  one  in  the  leaves,  one 
in  the  flowers,  and  a  third  in  the  rind  of  the  fruit. 

Notwithstanding  the  great  number  of  bodies  thus 
occurring  in  the  vegetable  kingdom,  it  is  a  few  which 
form  the  bulk  of  all  plants,  and  especially  of  those  which 
have  an  agricultural  importance  as  sources  of  food  to 
man  and  animals.  These  substances,  into  which  any 
plant  may  be  resolved  by  simple,  partly  mechanical  means, 
are  conveniently  termed  proximate  principles,  and  we 
shall  notice  them  in  some  detail  under  eight  principal 
classes,  viz.: 

1.  WATER. 

2.  The  CARBHYDRATES. 

3.  The  VEGETABLE  ACIDS. 

4.  The  FATS  and  OILS. 

5.  The  ALBUMINOIDS  or  PROTEIN  BODIES  and  FER- 
MENTS. 

6.  The  AMIDES. 

7.  The  ALKALOIDS. 

8.  PHOSPHORIZED  SUBSTANCES. 

i.  Water,  H20,  as  already  stated,  is  the  most  abund- 
ant ingredient  of  plants.  It  is  itself  a  compound  of 
oxygen  and  hydrogen,  having  the  following  centesimal 
composition : 


THE  VOLATILE  PART  OF  PLANTS. 


39 


Oxygen  ... 
Hydrogen . 


88.89 
11.11 


100.00 

It  exists  in  all  parts  of  plants,  is  the  immediate  cause 
of  the  succulence  of  their  tender  portions,  and  is  essen- 
tial to  the  life  of  the  vegetable  organs. 

In  the  following  table  are  given  the  percentages  of  water  in  some  of 
the  more  common  agricultural  products  in  the  fresh  state,  but  the  pro- 
portions are  not  quite  constant,  even  in  the  same  part  of  different 
specimens  of  any  given  plant. 

WATEB  IN  FRESH  PLANTS.    (PER  CENT.) 

Average. 

Meadow  grass 71 

Red  clover 80 

Maize,  as  used  for  fodder 82 

Cabbage 85 

Potato  tubers 75 

Sugar  beets 81 


Range. 
60  to  78 


Carrots 86 

Turnips 91 


In  living  plants,  water  is  usually  perceptible  to  the 
eye  or  feel,  as  sap.  But  it  is  not  only  fresh  plants  that 
contain  water.  When  grass  is  made  into  hay,  the  water 
is  by  no  means  all  dried  out,  but  a  considerable  propor- 
tion remains  in  the  pores,  which  is  not  recognizable  by 
the  senses.  So,  too,  seasoned  wood,  flour,  and  starch, 
when  seemingly  dry,  contain  a  quantity  of  invisible 
water,  which  can  be  removed  by  heat. 

EXP.  21.— Into  a  wide  glass  tube,  like  that  shown  in  Fig.  2,  place  a 
spoonful  of  saw  dust,  or  starch,  or  a  little  hay.  Warm  over  a  lamp, 
but  very  slowly  and  cautiously,  so  as  not  to  burn  or  blacken  the  sub- 
stance. Water  will  be  expelled  from  the  organic  matter,  and  will  col- 
lect on  the  cold  part  of  the  tube. 

It  is  thus  obvious  that  vegetable  substances  may  con- 
tain water  in  at  least  two  different  conditions.  Red 
clover,  for  example,  when  growing  or 
freshly  cut,  contains  about  80  per  cent  of 
water.  When  the  clover  is  dried,  as  for 
making  hay,  the  greater  share  of  this  wa- 
ter escapes,  so  that  the  air-dry  plant  con- 
tains but  about  15  per  cent.  On  subject- 
ing the  air-dry  clover  to  a  temperature 


Fig.  9. 


of  212  °  for  some  hours,  the  water  is  completely  expelled, 
and  the  substance  becomes  really  dry,  i.  e.,  water-free. 


40  HOW  CROPS  GROW. 

To  drive  off  all  water  from  vegetable  matters,  the  chemist  usually 
employs  a  water-oven,  Fig.  9,  consisting  of  a  vessel  of  tin  or  copper 
plate,  with  double  walls,  between  which  is  a  space  that  may  be  half 
filled  with  water.  The  substance  to  be  dried  is  placed  in  the  interior 
chamber,  the  door  is  closed,  and  the  water  is  brought  to  boil  by  the 
heat  of  a  lamp  or  stove.  The  precise  quantity  of  water  belonging  to, 
or  contained  in,  a  substance,  is  ascertained  by  first  weighing  the  sub- 
stance, then  drying  it  until  its  weight  is  constant.  The  loss  is  water. 

In  the  subjoined  table  are  given  the  average  quantities,  per  cent,  of 
water  existing  in  various  vegetable  products  when  air-dry. 

WATER   IN   AIB-DKY  PLANTS.  PER  CENT. 

Meadow  grass  (hay) 15 

Red  clover  hay 17 

Pine  wood 20 

Straw  and  chaff  of  wheat,  rye,  etc 15 

Bean  straw 18 

Wheat  (rye,  oat)  kernel 14 

Maize  kernel 12 

That  portion  of  the  water  which  the  fresh  plant  loses 
by  mere  exposure  to  the  air  is  chiefly  the  water  of  its 
juices  or  sap,  and,  on  crushing  the  fresh  plant,  is  mani- 
fest to  the  sight  and  feel  as  a  liquid.  It  is,  properly  speak- 
ing, the  free  water  of  vegetation.  The  water  which 
remains  in  the  air-dry  plant  is  imperceptible  to  the  senses 
while  in  the  plant, — can  only  be  discovered  on  expelling 
it  by  heat  or  otherwise, — and  may  be  designated  as  the 
hygroscopic  or  combined  water  of  vegetation. 

The  amount  of  water  contained  in  either  fresh  or  air- 
dry  vegetable  matter  is  somewhat  fluctuating,  according 
to  the  temperature  and  the  dryness  of  the  atmosphere. 

2.  The  Carbhydrates.  This  group  falls  into  three 
subdivisions,  viz.  : 

a.  THE  AMYLOSES,  comprising  Cellulose,  Starch,  Inu- 
lin,  Glycogen,  the  Dextrins  and  Gums,  having  the 
formula  (C6Hi005)n. 

~b.  THE  GLUCOSES,  which  include  Dextrose,  Levulose, 
Galactose  and  similar  sugars,  having  the  composition 
C6Hi206. 

c.  THE  SUCROSES,  viz. :  Cane  Sugar  or  Saccharose, 
Maltose,  Lactose  and  other  sugars,  whose  formula  iu 
most  cases  is  Cl2H22On. 


THE  VOLATILE  PART  OF  PLANTS.         41 

On  account  of  their  abundance  and  uses  the  Carbhy- 
drates  rank  as  the  most  important  class  of  vegetable  sub- 
stances. Their  name  refers  to  the  fact  that  they  consist 
of  Carbon,  Hydrogen  and  Oxygen,  the  last  two  elements 
being  always  present  in  the  same  proportions  that  are 
found  in  water. 

These  bodies,  especially  cellulose  and  starch,  form  by 
far  the  larger  share — perhaps  seven-eighths — of  all  the  dry 
matter  of  vegetation,  and  most  of  them  are  distributed 
throughout  all  parts  of  plants. 

a.   The  Amyloses. 

Cellulose  (CjH1005)n. — Every  agricultural  plant  is 
an  aggregate  o.f  microscopic  cells,  i.  e.,  is  made  up  of 
minute  sacks  QY  closed  tubes,  adhering  to  each  other. 

Fig.  10  reprs?e^its  an  extremely  thin  slice  from  the  stem  of  a  cabbage, 
magnified  230  diameters.  The  united  walls  of  two  cells  are  seen  in  sec- 
tion at  a,  whale  at  6  an  empty  space  is  noticed. 


Fig.  10. 


The  crater  coating,  or  wall,  of  the  vegetable  cell  con- 
sists chiefly  or  entirely  of  cellulose.  This  substance  is 
accordingly  the  skeleton  or  framework  of  the  plant,  and 
the  material  that  gives  toughness  and  solidity  to  its  parts. 
Next  to  water  it  is  the  most  abundant  body  in  the  vege- 
table world. 


3  HOW  CHOPS  GROW. 

Nearly  all  plants  and  all  their  parts  contain  cellulose, 
but  it  is  relatively  most  abundant  in 
stems  and  leaves.  In  seeds  it  forms  a 
large  portion  of  the  husk,  shell,  or  other 
outer  coating,  but  in  the  interior  of  the 
seed  it  exists  in  small  proportion. 

The  fibers  of  cotton  (Fig.  11,  a),  hemp, 
and  flax  (Fig.  11,  J),  and  white  cloth  and 
unsized  paper  made  from  these  materials, 
are  nearly  pure  cellulose. 

The  fibers  of  cotton,  hemp,  and  flax  are  simply 
long  and  thick-walled  cells,  the  appearance  of 
which,  when  highly  magnified,  is  shown  in  Fig.  11 
where  a  represents  the  thinner,  more  soft,  and  col 
lapsed  cotton  fiber,  and  6  the  thicker  and  more  due 
able  fiber  of  linen. 

Wood,  or  woody  fiber,  consists  of  long 
and  slender  cells  of  various  forms  and  di- 
mensions  (see  p.  293),  which  are  delicate 
when  young  (in  the  sap  wood),  but  as. 
they  become  older  fill  up  interiorly  by  the  deposition  of  re 
peated  layers  of  cellulose,  which  is  more  or  less  inter- 
grown  with  other  substances.*  The  hard  shells  of  nuts 
and  stone  fruits  contain  a  basis  of  cellulose,  which  is  im- 
pregnated with  other  matters. 

When  quite  pure,  cellulose  is  a  white,  often  silky  or 
spongy,  and  translucent  body,  its  appearance  varying 

*  Wood  was  formerly  supposed  to  consist  of  cellulose  and  so-called 
"lignin."  On  this  view,  according  to  F.  Schulze,  lignin  impregnates 
(not  simply  incrusts)  the  cell-wall,  is  soluble  in  hot  alkaline  solutions, 
and  is  readily  oxidized  by  nitric  acid.  Schulze  ascribes  to  it  the  com- 
position 

Carbon 55.3 

Hydrogen 5.8 

Oxygen 38.9 

100.0 

This  is,  however,  simply  the  inferred  composition  of  what  is  left  after 
the  cellulose,  etc.,  have  been  removed.  "  Lignin  "  cannot  be  separated 
in  the  pure  state,  and  has  never  been  analyzed.  What  is  thus  desig- 
nated is  a  mixture  of  several  distinct  substances.  Fremy's  lignose,  lig- 
none,  lignin,  and  lignireose,  as  well  as  J.  Erdman's  glycolignose  and 
liguose,  are  not  established  as  chemically  distinct  substances. 


THE  VOLATILE  PAET  OF  PLANTS.  43 

somewhat  according  to  the  source  whence  it  is  obtained. 
In  the  air-dry  state,  at  common  temperatures,  it  usually 
contains  about  10  %  of  hygroscopic  water.  It  has,  in 
common  with  animal  membranes,  the  character  of  swell- 
ing up  when  immersed  in  water,  from  imbibing  this 
liquid  ;  on  drying  again,  it  shrinks  in  bulk.  It  is  tough 
and  elastic. 

Cellulose,  as  it  naturally  occurs,  for  the  most  part  dif- 
fers remarkably  from  the  other  bodies  of  this  group,  in 
the  fact  of  its  slight  solubility  in  dilute  acids  and  alkalies. 
It  is  likewise  insoluble  in  water,  alcohol,  ether,  the  oils, 
and  in  most  ordinary  solvents.  It  is  hence  prepared  in 
a  state  of  purity  by  acting  upon  vegetable  tissues  con- 
taining it,  with  successive  solvents,  until  all  other  mat- 
ters are  removed. 

The  "skeletonized"  leaves,  fruit  vessels,  etc.,  which  compose  those 
beautiful  objects  called  phantom  bouquets,  are  commonly  made  by  dis- 
solving away  the  softer  portions  of  fresh  succulent  plants  by  a  hot  solu- 
tion of  caustic  soda,  and  afterwards  whitening  the  skeleton  of  fibers 
fliat  remains  by  means  of  chloride  of  lime  (bleaching  powder).  They 
are  almost  pure  cellulose. 

Skeletons  may  also  be  prepared  by  steeping  vegetable  matters  in  a 
Aixture  of  potassium  chlorate  and  dilute  nitric  acid  for  a  number  of 


EXP.  22.—  To  500  cubic  centimeters*  (or  one  pint)  of  nitric  acid  of  dens- 
ity 1.1,  add  30  grams  (or  one  ounce)  of  pulverized  potassium  chlorate, 
and  dissolve  the  latter  by  agitation.  Suspend  in  this  mixture  a  num- 
ber of  leaves,  etc.,t  and  let  them  remain  undisturbed,  at  a  temperature 
not  above  65°  F.,  until  they  are  perfectly  whitened,  which  may  require 
from  10  to  20  days.  The  skeletons  should  be  floated  out  from  the 
solution  on  slips  of  paper,  washed  copiously  in  clear  water,  and  dried 
under  pressure  between  folds  of  unsized  paper. 

The  fibers  of  the  whiter  and  softer  kinds  of  wood  are  now  much  em- 
ployed in  the  fabrication  of  paper.  For  this  purpose  the  wood  is  rasped 


*  On  subsequent  pages  we  shall  make  frequent  \ise  of  some  of  the 
French  decimal  weights  and  measures,  for  the  reasons  that  they  are 
much  more  convenient  than  the  English  ones,  and  are  now  almost  ex- 
clusively employed  in  all  scientific  treatises  and  investigations.  For 
small  weights,  the  gram,  abbreviated  gm.  (equal  to  15£  grains,  nearly), 
is  the  customary  unit.  The  unit  of  measure  by  volume  is  the  cubic  cen- 
timeter, abbreviated  c.  c.  (30  c.  c.  equal  one  fh'iid  ounce  nearly).  Gram 
weights  and  glass  measures  graduated  into  cubic  centimeters  are  fur- 
nished by  all  dealers  in  chemical  apparatus. 

t  Full-grown  but  not  old  leaves  of  the  elm,  maple,  and  maize,  heads  of 
unripe  grain,  slices  of  the  stem  and  joints  of  maize,  etc.,  may  be  em- 
ployed to  furnish  skeletons  that  will  prove  valuable  in  the  study  of  th« 
structure  of  these  organs. 


44  HOW  CROPS  GKOW. 

to  a  coarse  powder  by  machinery,  then  heated  with  a  wsak  soda  lye, 
and  finally  bleached  with  chloride  of  lime. 

Though  cellulose  is  insoluble  in,  or  but  slightly  affected 
by,  weak  or  dilute  acids  and  alkalies,  it  is  altered  and  dis- 
solved by  these  agents,  when  they  are  concentrated  or 
hot.  The  result  of  the  action  of  strong  acids  and  alka- 
lies is  various,  according  to  their  kind  and  the  degree  of 
strength  in  which  they  are  employed. 

Cellulose  Nitrates. — Strong  nitric  acid  transforms 
cellulose  into  various  cellulose  nitrates  according  to  its 
concentration.  In  these  bodies  portions  of  the  hydrogen 
and  oxygen  of  cellulose  are  replaced  by  the  atomic  group 
(radicle),  N03.  Cellulose  hexanitrate,  C12H14  (N03)6010, 
is  employed  as  an  explosive  under  the  name  gun  cotton. 
The  collodion  employed  in  photography  is  a  solution 
in  ether  of  the  penta-  and  tetranitrates,  C12H15(N03)5Oio 
and  Ci2H16(N03)4010.  Sodium  hydroxide  changes  these 
cellulose  nitrates  into  cellulose  and  sodium  nitrate. 

Hot  nitric  acid  of  ordinary  strength  destroys  cellulose 
by  oxidizing  it  with  final  formation  of  carbon  dioxide 
gas  and  oxalic  acid. 

Cellulose  Sulphates. — "When  cold  sulphuric  acid 
acts  on  cellulose  the  latter  may  either  remain  apparently 
unaltered  or  swell  up  to  a  pasty  mass,  or  finally  dissolve 
to  a  clear  liquid,  according  to  the  strength  of  the  acid, 
the  time  of  its  action,  and  the  quality  (density)  of  the 
cellulose.  In  excess  of  strong  oil  of  vitriol,  cellulose 
(cotton)  gradually  dissolves  with  formation  of  various 
cellulose  sulphates,  in  which  OH  groups  of  the  cellulose 
are  replaced  by  S04  of  sulphuric  acid.  These  sulphates 
are  soluble  in  water  and  alcohol,  and  when  boiled  with 
water  easily  decompose,  reproducing  sulphuric  acid,  but 
not  cellulose.  Instead  of  the  latter,  dextrin  and  dextrose 
(grape  sugar)  appear. 

Soluble  Cellulose,  or  Amyloid. — In  a  cooled  mix- 
ture of  oil  of  vitriol,  with  about  ^  its  volume  of  water, 


THE  VOLATILE  PART  OF  PLANTS.  45 

cellulose  dissolves.  On  adding  much  water  to  the  solu- 
tion there  separates  a  white  substance  which  has  the  same 
composition  as  cellulose,  but  is  readily  converted  into 
dextrin  by  cold  dilute  acid.  This  form  of  cellulose  as- 
sumes a  fine  blue  color  when  put  in  contact  with  iodine- 
tincture  and  sulphuric  acid. 

EXP.  23.— Fill  a  large  test-tube  first  with  water  to  the  depth  of  two  or 
three  inches.  Then  add  gradually  three  times  that  bulk  of  oil  of  vitriol, 
and  mix  thoroughly.  When  well  cooled  pour  a  part  of  the  liquid  on  a 
slip  of  unsized  paper  in  a  saucer.  After  some  time  the  paper  is  seen  to 
swell  up  and  partly  dissolve.  Now  flow  it  with  solution  of  iodine,* 
when  these  dissolved  portions  will  assume  a  fine  and  intense  blue  color. 
This  deportment  is  characteristic  of  cellulose,  and  may  be  employed 
for  its  recognition  under  the  microscope.  If  the  experiment  be  re- 
peated, using  a  larger  proportion  of  acid,  and  allowing  the  action  to 
continue  for  a  considerably  longer  time,  the  substance  producing  the 
blue  color  is  itself  destroyed,  and  addition  of  iodine  has  no  effect.f  Un- 
altered cellulose  gives  with  iodine  a  yellow  color. 

Paper  superficially  converted  into  amyloid  constitutes  vegetable 
parchment,  which  is  tough  and  translucent,  much  resembling  bladder, 
and  very  useful  for  various  purposes,  among  others  as  a  substitute  for 
sausage  "  skins." 

EXP.  24.— Into  the  remainder  of  the  cold  acid  of  Exp.  23  dip  a  strip  of 
unsized  paper,  and  let  it  remain  for  about  15  seconds ;  then  remove,  and 
rinse  it  copiously  in  water.  Lastly,  soak  some  minutes  in  water,  to 
which  a  little  ammonia  is  added,  and  wash  again  with  pure  water. 
These  washings  are  for  the  purpose  of  removing  the  acid.  The  success 
of  this  process  for  obtaining  vegetable  parchment  depends  upon  the 
proper  strength  of  the  acid,  and  the  time  of  immersion.  If  need  be, 
repeat,  varying  these  conditions  slightly,  until  the  result  is  obtained. 

The  denser  and  more  impure  forms  of  cellulose,  as  they 
occur  in  wood  and  straw,  are  slowly  acted  upon  by  chem- 
ical agents,  and  are  not  easily  digestible  by  most  animals ; 
but  the  cellulose  of  young  and  succulent  stems,  leaves, 
and  fruits  is  digestible  to  a  large  extent,  especially  by 
animals  which  naturally  feed  on  herbage,  and  therefore 
cellulose  is  ranked  among  the  nutritive  ingredients  of 
cattle-food. 

Chemical  composition  of  cellulose. — This  body  is  acom- 

*  Dissolve  a  fragment  of  iodine  as  large  as  a  wheat  kernel  in  20  c.  c.  of 
alcohol,  and  add  100  c.  c.  of  water  to  the  solution. 

t  According  to  Grouven,  cellulose  prepared  from  rye  straw  (and  im- 
pure?) requires  several  hours'  action  of  sulphuric  acid  before  it  will 
strike  a  blue  color  with  iodine  (Zter  Salsmunder  liericht,  p.  467). 


46  HOW  CHOPS  GEOW. 

pound  of  the  three  elements,  carbon,  oxygen,  and  hydro- 
gen. Analyses  of  it,  as  prepared  from  a  multitude  of 
sources,  demonstrate  that  its  composition  is  expressed  by 
the  formula  (C6  H10  Os)n.  The  value  of  n  in  this  form- 
ula is  not  certainly  known,  but  is  at  least  two,  and  the 
formula  C12H20Oio  is  very  commonly  adopted.  In  100 
parts  it  contains 

Carbon 44.44 

Hydrogen 6.17 

Oxygen 49.39 

100.00 

Modes  of  estimating  cellulose. — In  statements  of  the  composition  of 
plants,  the  terms  fiber,  woody  fiber,  and  crude  cellulose  are  often  met 
with.  These  are  applied  to  more  or  less  impure  cellulose,  which  is  ob- 
ta'ned  as  a  residue  after  removing  other  matters,  as  far  as  possible,  by 
alternate  treatment  with  dilute  acids  and  alkalies.  The  methods  are 
Confessedly  imperfect,  because  cellulose  itself  is  dissolved  to  some  ex- 
tent, and  a  portion  of  other  matters  often  remains  unattacked. 

The  method  of  Henneberg,  usually  adopted  ( Vs.  St., VI,  407),  is  as  follows : 
-igrams  of  the  finely  divided  substance  are  boiled  for  half  an  hour  with 
JOO  cubic  centimeters  of  dilute  sulphuric  acid  (containing  l\  per  cent  of 
tal  of  vitriol),  and,  after  the  substance  has  settled,  the  acid  liquid  is 
youred  off.  The  residue  is  boiled  again  for  half  an  hotir  with  200  c.  c.  of 
dilute  potash  lye  (containing  1J  per  cent  of  dry  caustic  potash),  and,  after 
removing  the  alkaline  liquid,  it  is  boiled  twice  with  water  as  before. 
What  remains  is  brought  upon  a  filter,  and  washed  with  water,  then 
with  alcohol,  and,  lastly,  with  ether,  as  long  as  these  solvents  take 
up  anything.  This  crude  cellulose  contains  ash  and  nitrogen,  for  which 
corrections  must  be  made.  The  nitrogen  is  assumed  to  belong  to  some 
albuminoid,  and  from  its  quantity  the  amount  of  the  latter  is  calcu- 
lated ;  (see  p.  113). 

Even  with  these  corrections,  the  quantity  of  cellulose  is  not  obtained 
with  entire  accuracy,  as  is  usually  indicated  by  its  appearance  and  its 
composition.  While  the  crude  cellulose  thus  prepared  from  the  pea  is 
perfectly  white,  that  from  wheat  bran  is  brown,  and  that  from  rape- 
cake  is  almost  black  in  color,  from  impurities  that  cannot  be  removed 
by  this  method. 

Grouven  gives  the  following  analyses  of  two  samples  of  crude  cellu- 
lose obtained  by  a  method  essentially  the  same  as  we  have  described. 
(2ter  Salzmunder  Bericht,  p.  456.) 

Rye-straw  fiber.       Flax  fiber. 

Water. 8.65  5.40 

Ash 2.05  1.14 

N 0.15  0.15 

C 42.47  38.36 

H. 6.04  5.89 

0 40.64  48.95 


100.00  100.00 

On  deducting  water  and  ash,  and  making  proper  correction  for  the 


THE  VOLATILE  PAKT  OF  PLANTS.  4? 


nitrogen,  the  above  samples,  together  with  one  of  wheat-straw  fiber, 
analyzed  by  Henneberg,  exhibit  the  following  composition,  compared 
with  pure  cellulose. 

Eye-straw  fiber.    Flax  fiber.   Wheat-straw  fiber.  Pure  cellulose. 
C  ..  47.5  41.0  45.4  44.4 

H...  ....     6.8  6.4  6.3  6.2 

0 45.7  62.6  48.3  49.4 

100.0  100.0  100.0  100.0 

Fr.  Schulze  has  proposed  (1857)  another  method  for  estimating  cellu- 
lose, which,  though  troublesome,  is  in  most  cases  more  correct  than  the 
one  already  described.  Kiihn,  Aronstein,  and  H.  Schulze  (Henneberg's 
Journal  fur  Landwirthschaft,  1866,  pp.  289  to  297)  have  applied  this 
method  in  the  following  manner :  One  part  of  the  dry  pulverized  sub- 
stance (2  to  4  grams),  which  has  been  previously  extracted  with  water, 
alcohol,  and  ether,  is  placed  in  a  glass-stoppered  bottle,  with  0.8  part 
of  potassium  chlorate  and  12  parts  of  nitric  acid  of  specific  gravity  1.10, 
and  digested  at  a  temperature  not  exceeding  65°  F.  for  14  days.  At  the 
expiration  of  this  time,  the  contents  of  the  bottle  are  mixed  with  some 
water,  brought  upon  a  filter,  and  washed,  firstly,  with  cold  and  after- 
wards with  hot  water.  When  all  the  acid  and  soluble  matters  have 
been  washed  out,  the  contents  of  the  filter  are  emptied  into  a  beaker, 
and  heated  to  165°  F.  for  about  45  minutes  with  weak  ammonia  (1  part 
commercial  ammonia  to  50  parts  of  water);  the  substance  is  then 
brought  upon  a  weighed  filter,  and  washed,  first,  with  dilute  ammonia, 
as  long  as  this  passes  off  colored,  then  with  cold  and  hot  water,  then 
with  alcohol,  and,  finally,  with  ether.  The  substance  remaining  con- 
tains a  small  quantity  of  ash  and  nitrogen,  for  which  corrections  must 
be  made.  The  fiber  is,  however,  purer  than  that  procured  by  the  other 
method,  and  the  writers  named  obtained  a  somewhat  larger  quantity, 
by  J  to  H  per  cent.  The  results  appear  to  vary  but  about  one  per  cent 
from  the  truth.  The  observations  of  Konig  (Vs.  St.  16),  and  of  Hoffmeis- 
ter  (Vs.  St.  33, 155),  show  much  larger  differences  in  favor  of  Fr.  Schulze's 
method. 

Hugo  Muller  (Die  Pflanzenfaser,  p.  27)  has  described  a  method  of  ob- 
taining cellulose  from  those  materials  which  are  employed  in  paper- 
making,  which  is  based  on  the  prolonged  use  of  weak  aqueous  solu- 
tion of  bromine. 

Trials  made  on  hay  and  Indian-corn  fodder  with  this  method  by  Dr. 
Osborne,  at  the  author's  suggestion,  gave  results  widely  at  variance 
with  those  obtained  by  Henneberg's  method. 

The  average  proportions  of  cellulose  found  in  various 
vegetable  matters,  in  the  usual  or  air-dry  state,  are  as  fol- 
lows : 

AMOUNT  OF  CELLULOSE  IN  PLANTS. 

Per  cent.  Per  cent. 

Potato  tuber 1.1  Red  clover  plant  in  flower —  10 

Wheatkernel 3.0          "         "      hay 34 

Wheatmeal. 0.7       Timothy 23 

Maize  kernel 5.5       Maize  cobs 38 

Barley      "       8.0       Oat  straw 40 

Oat  "       10.3       Wheat"     48 

Buckwheat  kernel 15.0       Rye      "    84 


48  HOW  CROPS  GROW. 

Starch  (C6H1005)n  is  of  very  general  occurrence  in 
plants.  The  cells  of  the  seeds  of  wheat,  corn,  and  all 
other  grains,  and  the  tubers  of  the  potato,  contain  this 
familiar  body  in  great  abundance.  It  occurs  also  in  the 
wood  of  all  forest  trees,  especially  in  autumn  and  winter. 
It  accumulates  in  extraordinary  quantity  in  the  pith  of 
some  plants,  as  in  the  Sago-palm  (Sagus  Rttmphii),  of 
the  Malay  Islands,  a  single  tree  of  which  may  yield  800 
pounds.  The  onion,  and  various  plants  of  the  lily  tribe, 
are  said  to  be  entirely  destitute  of  starch. 

The  preparation  of  starch  from  the  potato  is  very  sim- 
ple. The  potato  tuber  contains  about  70  per  cent,  water, 
24  per  cent  starch,  and  1  per  cent  of  cellulose,  while  the 
remaining  5  per  cent  consist  mostly  of  matters  which 
are  easily  soluble  in  water.  By  grating,  the  potatoes  are 
reduced  to  a  pulp;  the  cells  are  thus  broken  and  the 
starch-grains  set  at  liberty.  The  pulp  is  agitated  on  a 
fine  sieve,  in  a  stream  of  water.  The  washings  run  off 
milky  from  suspended  starch,  while  the  cell-tissue  is  re- 
tained by  the  sieve.  The  milky  liquid  is  allowed  to  rest 
in  vats  until  the  starch  is  deposited.  The  water  is  then 
poured  off,  and  the  starch  is  collected  and  dried. 

Wheat-starch  may  be  obtained  by  allowing  wheaten 
flour  mixed  with  water  to  ferment  for  several  weeks.  In 
this  process  the  gluten,  etc.,  are  converted  into  soluble 
matters,  which  are  removed  by  washing,  from  the  unal- 
tered starch. 

Starch  is  now  most  largely  manufactured  from  maize. 
A  dilute  solution  of  caustic  soda  is  used  to  dissolve  the 
albuminoids  (see  p.  87).  The  starch  and  bran  remaining 
are  separated  by  diffusing  both  in  water,  when  the  bran 
rapidly  settles,  and  the  water,  being  run  off  at  the  proper 
time,  deposits  nearly  pure  starch,  the  corn-starch  of  com- 
merce. 

Starch  is  prepared  by  similar  methods  from  rice,  horse- 
chestnuts,  and  various  other  plants. 


THE  VOLATILE  PAET  OF   PLANTS.  49 

Arrow-root  is  starch  obtained  by  grating  and  washing 
the  root-sprouts  of  Maranta  Indica,  and  M.  arundinacea, 
plants  native  to  the  East  and  West  Indies. 

EXP.  25.— Reduce  a  clean  potato  to  pulp  by  means  of  a  tin  grater.  Tie 
up  the  pulp  in  a  piece  of  not  too  fine  muslin,  and  squeeze  it  repeatedly 
in  a  quart  or  more  of  water.  The  starch  grains  thus  pass  the  meshes  of 
the  cloth,  while  the  cellulose  is  retained.  Let  the  liquid  stand  until 
the  starch  settles,  pour  off  the  water,  and  dry  the  residue. 

Starch,  as  usually  seen,  is  either  a  white  powder  which 
consists  of  minute,  rounded  grains,  and  hence  has  a 
slightly  harsh  feel,  or  occurs  in  5  or  6-sided  columnar 
masses  which  readily  crush  to  a  powder.  Columnar 
starch  acquires  that  shape  by  rapid  drying  of  the  wet 
substance.  When  observed  under  a  powerful  magnifier, 
the  starch-grains  often  present  characteristic  forms  and 
dimensions. 

In  potato-starch  they  are  egg  or  kidney-shaped,  and 
are  distinctly  marked  with  curved  lines  or  ridges,  which 


Fig.  12. 


surround  a  point  or  eye  ;  a,  Fig.  12.  Wheat-starch  con- 
sists of  grains  shaped  like  a  thick  burning-glass,  or  spec- 
tacle-lens, having  a  cavity  in  the  centre,  J.  Oat-starch 
is  made  up  of  compound  grains,  which  are  easily  crushed 
into  smaller  granules,  c.  In  maize  and  rice  the  grains 
are  usually  so  densely  packed  in  the  cells  as  to  present  an 
angular  (six-sided)  outline,  as  in  d.  The  starch  of  the 
bean  and  pea  has  the  appearance  of  e.  The  minute 


50  HOW  CROPS  GROW. 

starch-grains  of  the  parsnip  are  represented  at  /,  and 
those  of  the  beet  at  g. 

The  grains  of  potato-starch  are  among  the  largest,  be- 
ing often  5£o  of  an  inch  in  diameter;  wheat-starch 
grains  are  about  y^^  of  an  inch ;  those  of  rice,  ^^^  of 
an  inch,  while  those  of  the  beet-root  are  still  smaller. 

The  starch-grains  have  an  organized  structure,  plainly 
seen  in  those  from  the  potato,  which  are  marked  with 
curved  lines  or  ridges  surrounding  a  point  or  eye  ;  a,  Fig. 
12.  When  a  starch-grain  is  heated  cautiously,  it  swells 
and  exfoliates  into  a  series  of  more  or  less  distinct  layers. 

Starch,  when  air-dry,  contains  a  considerable  amount  of 
water,  which  may  range  from  12  to  23  per  cent.  Most  of 
this  water  escapes  readily  when  starch  is  dried  at  212°, 
but  a  temperature  of  230°  F.  is  needful  to  expel  it  com- 
pletely. Starch,  thus  dried,  has  the  same  composition 
in  100  parts  as  cellulose,  yiz. : 

Carbon 44.44 

Hydrogen 6.17 

Oxygen 49.39 

100.00 

Starch-grains  are  unacted  upon  by  cold  water,  unless 
broken  (see  Exp.  26),  and  quickly  settle  from  suspension 
in  it,  having  a  specific  gravity  of  1. 5. 

Iodine-Test  for  Starch. — The  chemist  is  usually  able  to 
recognize  starch  with  the  greatest  ease  and  certainty  by 
its  peculiar  deportment  towards  iodine,  which,  when  dis- 
solved in  water  or  alcohol  and  brought  in  contact  with 
starch-grains,  most  commonly  gives  them  a  beautiful 
blue  or  violet  color.  This  test  may  be  used  even  in 
microscopic  observations  with  the  utmost  facility.  Some 
kinds  of  starch-grains  are,  however,  colored  red,  some 
yellow,  and  a  few  brown,  probably  because  of  the  pres- 
ence of  other  substances. 

EXP.  26. — Shake  together  in  a  test-tube  30  c.  c.  of  water  and  starch 
of  the  bulk  of  a  kernel  of  maize.  Add  solution  of  iodine  drop  by  drop, 
agitating  until  a  faint  purplish  color  appears.  Pour  off  half  the  liquid 


THE  VOLATILE  PART  OF  PLAKfS.  51 

Into  another  test-tube,  and  add  at  once  to  it  one-fourth  its  bulk  of 
iodine  solution.  The  latter  portion  becomes  intensely  blue  by  trans- 
mitted, or  almost  black  by  reflected,  light.  On  standing,  observe  that 
In  the  first  case,  where  starch  preponderates,  it  settles  to  the  bottom, 
leaving  a  colorless  liquid,  which  shows  the  insolubility  of  starch  in 
cold  water ;  the  starch  itself  has  a  purple  or  red  tint.  In  the  case 
iodine  was  used  in  excess,  the  deposited  starch  is  blue-black. 

By  the  prolonged  action  of  dry  heat,  hot  water,  acids, 
or  alkalies,  starch  is  converted  first  into  amidulin,  then 
into  dextrin,  and  finally  into  the  sugars  maltose  and  dex- 
trose, as  will  be  presently  noticed. 

Similar  transformations  are  accomplished  by  the  action 
of  living  yeast,  and  of  the  so-called  diastase  of  germinat- 
ing seeds. 

The  saliva  of  man  and  plant-eating  animals  likewise 
disintegrates  the  starch-grains  and  mostly  dissolves  the 
starch  by  converting  it  into  maltose  (sugar).  It  is  much 
more  promptly  converted  into  sugar  by  the  liquids  of  the 
large  intestine.  It  is  thus  digested  when  eaten  by  ani- 
mals. Starch  is,  in  fact,  one  of  the  most  important 
ingredients  of  the  food  of  man  and  domestic  animals. 

The  starch-grains  are  not  homogeneous.  After  pro- 
longed action  of  saliva,  hot  water,  or  of  dilute  acids  on 
starch-grains,  an  undissolved  residue  remains  which  De- 
Saussure  (1819)  regarded  as  nearly  related  to  cellulose. 
This  residue  is  not  changed  by  boiling  water,  but,  under 
prolonged  action  of  dilute  acids,  it  finally  dissolves. 
With  iodine,  after  treatment  with  strong  sulphuric  acid, 
it  gives  the  blue  color  characteristic  of  cellulose.  There- 
fore it  is  commonly  termed  starch-cellulose. 

Starch-cellulose  amounts  to  0.5  to  6  per  cent  of  the 
starch-grains,  varying  with  the  kind  of  starch  and  the 
nature  and  duration  of  the  solvent  action.  Whether  it 
be  originally  present  or  a  result  of  the  treatment  by 
acids,  etc.,  is  undecided. 

The  chemical  composition  of  starch-cellulose  is  identi- 
cal with  that  of  the  entire  starch-grain,  viz. :  (C6H1005)n. 

The  starch-grains  also  contain  a  small  proportion  of 
amidulin,  or  soluble  starch,  presently  to  be  noticed. 


62  HOW  CROPS  GROW. 


Gelatinous  Starch.  When  starch  is  heated  to  near  boiling  with  12  to 
15  times  its  weight  of  water,  the  grains  swell  and  burst,  or  exfoliate, 
the  water  is  absorbed,  and  the  whole  forms  a,  jelly.  This  is  the  starch- 
paste  used  by  the  laundress  for  stiffening  muslin.  The  starch  is  but 
very  slightly  dissolved  by  this  treatment.  On  freezing  gelatinous 
starch,  the  water  belonging  to  it  is  separated  as  ice  and  on  melting 
remains  for  the  most  part  distinct. 

EXP.  27. — Place  a  bit  of  starch  as  large  as  a  grain  of  wheat  in  30  c.  c. 
of  cold  water  and  heat  to  boiling.  The  starch  is  converted  into  thin, 
translucent  paste.  That  a  portion  is  dissolved  is  shown  by  filtering 
through  paper  and  adding  to  one-half  of  the  filtrate  a  few  drops  of 
iodine  solution,  when  a  perfectly  clear  blue  liquid  is  obtained.  The 
delicacy  of  the  reaction  is  shown  by  adding  to  30  c.  c.  of  water  a  little 
solution  of  iodine,  and  noting  that  a,  feu-  dro/»s  of  the  solution  of  starch 
suffice  to  make  the  large  mass  of  liquid  perceptibly  blue. 

When  starch-paste  is  dried,  it  forms  a  hard,  horn-like  mass. 

Tapioca  and  Sago  are  starch,  which,  from  being  heated  while  still 
moist,  is  partially  converted  into  starch-paste,  and,  on  drying,  acquires 
a  more  or  less  translucent  aspect.  Tapioca  is  obtained  from  the  roots 
of  various  kinds  of  Manihot,  cultivated  in  the  West  Indies  and  South 
America.  Cassava  is  a  preparation  of  the  same  starch,  roasted.  Sago 
is  made  in  the  islands  of  the  East  Indian  Archipelago,  from  the  pith  of 
palms  (Sagiis).  It  is  granulated  by  forcing  the  paste  through  metallic 
sieves.  Both  tapioca  and  sago  are  now  imitated  from  maize  starch. 

Next  to  water  and  cellulose,  starch  is  the  most  abund- 
ant ingredient  of  agricultural  plants. 

In  the  subjoined  table  are  given  the  proportions  of  starch  in  certain 
vegetable  products,  as  determined  by  Dr.  Dragendorff.  The  quantities 
are,  however,  somewhat  variable.  Since  the  figures  below  mostly 
refer  to  air-dry  substances,  the  proportions  of  hygroscopic  water  found 
in  the  plants  by  Dragendorff  are  also  given,  the  quantity  of  which, 
being  changeable,  must  be  taken  into  account  in  making  any  strict 
comparisons. 

AMOUNT  OF  STARCH  IK  PLANTS. 

Water.  Starch. 

Per  cent.  Per  cent. 

Wheat 13.2  59.5 

Wheatflour 15.8  68.7 

Rye 11.0  59.7 

Oats 11.9  46.6 

Barley 11.5  57.5 

Timothy-seed 12.6  45.0 

Rice  (hulled) 13.3  61.7 

Peas 5.0  37.3 

Beans(white) 16.7  33.0 

Clover-seed 10.8  10.8 

Plaxseed 7.6  23.4 

Mustard-seed 8.5  9.9 

Colza-seed 5.8  8.6 

Teltow  turnips* dry  substance  9.8 

Potatoes dry  substance  62.5 

*  A  sweet  and  mealy  turnip,  grown  011  light  soils,  for  table  use. 


THE  VOLATILE  PART  OF  PLANTS.        53 

Starch  Is  quantitatively  estimated  by  various  methods. 

1.  In  case  of  potatoes  or  cereal  grains,  it  may  be  determined  roughly 
by  direct  mechanical  separation.    For  this  purpose  5  to  20  grams  of  the 
substance  are  reduced  to  fine  division  by  grating  (potatoes)  or  by  sof- 
tening in  warm  water,  and  crushing  in  a  mortar  (grains).    The  pulp 
thus  obtained  is  washed  either  upon  a  fine  hair-sieve  or  in  a  bag  of 
muslin,  until  the  water  runs  off  clear.    The  starch  is  allowed  to  settle, 
is  dried,  and  weighed.    The  value  of  this  method  depends  upon  the  care 
employed  in  the  operations.    The  amount  of  starch  falls  out  too  low, 
because  it  is  impossible  to  break  open  all  the  minute  cells  of  the  sub- 
stance analyzed. 

2.  In  many  cases  starch  may  be  estimated  with  great  precision  by 
conversion  into  sugar.    For  this  purpose  Sachsse  heats  3  grams  of  air- 
dry  substance,  contained  in  a  flask  with  reflux  condenser,  in  a  boiling 
water  bath  for  3  hours,  with  200  c.  c.  of  water  and  20  c.  c.  of  a  25  per  cent 
hydrochloric  acid.    After  cooling,  the  acid  is  nearly  neutralized  with 
sodium  hydroxide,  and  the  dextrose  into  which  the  starch  has  been  con- 
verted is  determined  by  Allihn's  method,  described  on  p.  65.      Winton, 
Report  Ct.  Ag.  Exp.  St.,  1887,  p.  132. 

3.  For  Dragendorff s  method,  see  Henneberg's  Journal,  fur  Land- 
Wirthschaft,  1862,  p.  206. 

Amidulin,  or  Soluble  Starch. — A  substance  soluble 
in  cold  water  appears  to  exist  in  small  quantity  in  the  in- 
terior of  ordinary  starcb-grains.  It  is  not  extracted  by 
cold  water  from  tbe  unbroken  starch,  as  shown  by  Exp. 
26.  On  pulverizing  starch-grains  under  cold  water  by 
rubbing  in  a  mortar  with  sharp  sand,  the  water,  made 
clear  by  standing  or  filtration,  gives  with  iodine  the  char- 
acteristic blue  coloration.  Exp.  27  shows  that  when 
starch  is  gelatinized  by  hot  water,  as  in  making  starch 
paste,  a  small  quantity  of  starch  goes  into  actual  solu- 
tion. 

Ordinary  insoluble  starch  may  be  largely  converted 
into  soluble  starch  by  moderate  heating,  either  for  a  long 
time  to  the  temperature  of  boiling  water  or  for  a  short 
space  to  375°  F.  Maschke  obtained  a  perfectly  clear  solu- 
tion of  potato-starch  by  heating  it  with  30  times  its  bulk 
of  water  in  a  sealed  glass  tube  kept  immersed  for  8  days 
in  boiling  water.  Zulkowski  reached  the  same  result  by 
heating  potato-starch  (1  part)  with  commercial  glycerine 
(16  parts).  In  this  case  the  starch  at  first  swells  and 
the  mixture  acquires  a  pasty  consistence,  but,  when  the 


54  HOW  CEOPS  GROW. 

temperature  rises  to  375°  F.,  the  starch  dissolves  to  a 
nearly  clear  thin  liquid. 

Amidulin  also  appears  to  be  the  first  product  of  the 
action  of  diastase  (the  ferment  of  sprouting  seeds)  on 
starch  and  doubtless  exists  in  malt. 

Soluble  starch  is  colored  blue  by  iodine  and  is  thrown 
down  from  its  solution  in  water,  or  glycerine,  by  addition 
of  strong  alcohol.  It  redissolves  in  water  or  weak  alco- 
hol. Its  concentrated  aqueous  solutions  gelatinize  on 
keeping  and  the  jelly  is  no  longer  soluble  in  water. 
Dilute  solutions  when  evaporated  leave  a  transparent 
residue  that  is  insoluble  in  water. 

On  boiling  together  diluted  sulphuric  acid  and  starch 
the  latter  shortly  dissolves,  and  if  as  soon  as  solution  has 
taken  place,  the  acid  be  neutralized  with  carbonate  of 
lime  and  removed  by  filtration,  soluble  starch  remains 
dissolved.  (Schulze's  Amidulin.) 

Amylodextrln.  Nageli  has  described  as  Amylodextrin  I  and  Amylo- 
dextrin  II,  two  substances  that  result  from  the  action  of  moderately 
strong  acids  on  potato-starch  at  common  temperatures.  The  starch 
when  soaked  for  many  weeks  in  12%  hydrochloric  acid  remains  nearly 
unchanged  in  appearance,  but  the  interior  parts  of  the  grains  grad- 
ually dissolve  out,  being  changed  into  amylodextrin  II,  which  closely 
resembles  and  is  probably  identical  with  amidulin. 

The  starch-grains  that  remain  unchanged  in  outward  appearance,  if 
tested  with  iodine  solution  from  time  to  time,  are  at  first  colored  blue, 
but  after  some  days  they  take  on  a  violet  tinge  and  after  prolonged 
action  of  the  acid  are  made  red  and  finally  yellow  by  iodine.  The  grains, 
which  are  now  but  empty  shells,  may  be  freed  from  acid  by  washing 
with  cold  water,  and  then,  if  heated  to  boiling  with  pure  water,  they 
readily  dissolve  to  a  clear  solution  (amylodextrin  I),  from  which  Nageli, 
by  freezing  and  by  evaporation,  obtained  crystalline  disks.  These 
bodies,  when  dry,  have  the  same  composition  as  cellulose,  starch,  and 
amidulin. 

Dextrin  (CeH^Os)  was  formerly  thought  to  occur 
dissolved  in  the  sap  of  all  plants.  According  to  Von 
Bibra's  investigations,  the  substance  existing  in  bread- 
grains,  which  earlier  experimenters  believed  to  be  dex- 
trin, is  for  the  most  part  gum.  Busse,  who  examined 
yarious  young  cereal  plants  and  seeds,  and  potato  tubers, 
for  dextrin,  found  it  only  in  old  potatoes  and  young 


THE  VOLATILE  PART  OF  PLANTS.  55 

wheat  plants,  and  there  in  very  small  quantity.  Accord- 
ing to  Meissl,  the  soy  bean  contains  10  per  cent  of  dex- 
trin. 

Dextrin  is  easily  prepared  artificially  by  the  trans- 
formation of  starch,  or,  rather,  of  amidulin  derived  from 
starch,  and  its  interest  to  us  is  chiefly  due  to  this  fact. 
When  starch  is  exposed  some  hours  to  the  heat  of  an 
oven,  or  for  30  minutes  to  the  temperature  of  415°  F., 
the  grains  swell,  burst  open,  and  are  gradually  converted 
into  a  light-brown  substance,  which  dissolves  readily  in 
water,  forming  a  clear,  gummy  solution.  This  is  dex- 
trin, and  thus  prepared  it  is  largely  used  in  the  arts, 
especially  in  calico-printing,  as  a  cheap  substitute  for 
gum  arabic.  In  the  baking  of  bread  it  is  formed  from 
the  starch  of  the  flour,  and  often  constitutes  ten  per  cent 
of  the  loaf.  The  glazing  on  the  crust  of  bread,  or  upon 
biscuits  that  have  been  steamed,  is  chiefly  due  to  a  coat- 
ing of  dextrin.  Dextrin  is  thus  an  important  ingredient 
)f  those  kinds  of  food  which  are  prepared  from  the 
Starchy  grains  by  cooking. 

Commercial  dextrin  appears  either  in  translucent 
brown  masses  or  as  a  yellowish-white  powder.  On  ad- 
dition of  cold  water,  the  dextrin  readily  dissolves,  leaving 
oehind  a  portion  of  unaltered  starch.  When  the  solu- 
tion is  mixed  with  strong  alcohol,  the  dextrin  separates 
in  white  flocks.  With  iodine,  solution  of  commercial 
dextrin  gives  a  fine  purplish-red  color. 

There  are  doubtless  several  distinct  dextrins  scarcely  dis- 
tinguishable except  by  the  different  degrees  to  which  they 
affect  polarized  light  or  by  various  chemical  deportment 
(reducing  effect  on  alkaline  copper  solutions).  They  are 
characterized  as  erythrodextrins,  which  give  with  iodine 
a  red  color,  and  achroodextrins,  which  give  no  color  with 
iodine.  Investigators  do  not  agree  as  to  the  precise  num- 
ber of  dextrins  that  result  from  the  transformation  of 
starch. 


56  HOW  CROPS  GROW. 

EXP.  28. — Cautiously  heat  a  spoonful  of  powdered  starch  in  a  porce» 
lain  dish,  with  constant  stirring  so  that  it  may  not  burn,  for  the  space 
of  five  minutes;  it  acquires  a  yellow,  and  later,  a  brown  color.  Now 
add  thrice  its  bulk  of  water,  and  heat  nearly  to  boiling.  Observe  that 
a  slimy  solution  is  formed.  Pour  it  upon  a  filter;  the  liquid  that  runs 
through  contains  dextrin.  To  a  portion  add  twice  its  bulk  of  alcohol ; 
dextrin  is  precipitated.  To  another  portion,  add  solution  of  iodine ; 
this  shows  the  presence  of  dissolved  but  unaltered  starch.  To  a 
third  portion  of  the  filtrate  add  one  drop  of  strong  sulphuric  acid  and 
boil  a  few  minutes.  Test  with  iodine,  which,  as  soon  as  all  starch  is 
transformed,  will  give  a  red  instead  of  a  blue  color. 

Not  only  heat  but  likewise  acids  and  ferments  produce 
dextrins  from  starch  and,  according  to  some  authors, 
from  cellulose.  In  the  sprouting  of  seeds,  dextrin  is 
abundantly  formed  from  starch  and  hence  is  an  ingre- 
dient of  malb  liquors. 

The  agencies  that  convert  starch  into  the  dextrins  easily 
transform  the  dextrins  into  sugars  (maltose  or  dextrose), 
as  will  be  presently  noticed. 

The  chemical  composition  of  dry  dextrin  is  identical 
with  that  of  dry  cellulose,  starch,  and  amidulin. 

Inulin,  C36H62036,  closely  resembles  starch  in  many 
points,  and  appears  to  replace  that  body  in  the  roots  of 
the  American  artichoke,*  elecampane,  dahlia,  dandelion, 
chicory,  and  other  plants  of  the  same  natural  family 
(composite).  It  may  be  obtained  in  the  form  of  minute 
white  grains,  which  dissolve  easily  in  hot  water,  and  sep- 
arate again  as  the  water  cools.  According  to  Bouchar.dut, 
the  juice  of  the  dahlia  tuber,  expressed  in  winter,  becomes 
a  semi-solid  white  mass  after  reposing  some  hours,  from 
the  separation  of  8  per  cent  of  inulin. 

Inulin,  when  pure,  gives  no  coloration  with  iodine.  It 
may  be  recognized  in  plants,  where  it  occurs  as  a  solu- 
tion, usually  of  the  consistence  of  a  thin  oil,  by  soaking 
a  slice  of  the  plant  in  strong  alcohol.  Inulin  is  insolu- 
ble in  this  liquid,  and  under  its  influence  shortly  separ- 

*  Helianthus  tuberosiis,  commonly  known  as  Jerusalem  artichoke,  and 
cultivated  in  Europe  under  the  name  topmamhour,  is  a  native  of  the 
Northern  Mississippi  States. 


THE  VOLATILE  PART  OF  PLANTS.  57 

ates  as  a  solid  in  the  form  of  spherical  granules,  which 
may  be  identified  with  the  aid  of  the  microscope,  and 
have  an  evident  crystalline  structure. 

When  long  heated  with  water  it  is  slowly  but  complete- 
ly converted  into  a  kind  of  sugar  (levulose);  hot  dilute 
acids  accomplish  the  same  transformation  in  a  short 
time.  It  is  digested  by  animals,  and  doubtless  has  the 
same  value  for  food  as  starch. 

In  chemical  composition,  inulin,  dried  at  212°,  differs 
from  cellulose  and  starch  by  containing  for  six  times 
C6H1005,  the  elements  of  an  additional  molecule  of  water  ; 
C36H62036  =  6C6H1005  -f  H20  Kiliani. 

Levulin  (C6H1005)n  coexists  with  inulin  in  the  mature 
or  frozen  tubers  of  the  artichoke,  dahlia,  etc.,  and,  accord- 
ing to  Muentz,  is  found  in  unripe  rye-grain.  It  is  a  highly 
soluble,  tasteless,  gum-like  substance  resembling  dextrin, 
but  without  effect  on  polarized  light.  It  appears  to  be 
formed  from  inulin  when  the  latter  is  long  heated  with 
water  at  the  boiling  point,  or  when  the  tubers  contain- 
ing inulin  sprout.  Dilute  acids  readily  transform  it  into 
levulose,  as  they  convert  dextrin  into  dextrose. 

SrLYCOGEN  (C6H1005)n  exists  in  the  blood  and  mus- 
cles of  animals  in  small  quantity,  and  abundantly  in  the 
liver,  especially  soon  after  hearty  eating.  It  is  obtained 
by  boiling  minced  fresh  livers  with  water,  or  weak  potash 
solution,  and  adding  alcohol  to  the  filtered  liquid.  It  is 
A  white  powder  which,  with  water,  makes  an  opalescent 
solution.  It  is  colored  wine-red  by  iodine.  Boiling  di- 
lute sulphuric  acid  converts  it  into  dextrose.  With  saliva, 
it  is  said  to  yield  dextrin,  maltose  and  dextrose.  Accord- 
ing to  late  observations,  glycogen  occurs  in  the  vegetable 
kingdom,  having  been  identified  in  various  fungi  and  in 
plants  of  the  flax  and  the  potato  families. 

The  Gums  and  Pectin  Bodies. — A  number  of 
bodies  exist  in  the  vegetable  kingdom,  which,  from  the 
similarity  of  their  properties,  have  received  the  common 


58  HOW  CROPS  GROW. 

designation  of  gums.  The  best  known  are  Gum  Arabic, 
the  gums  of  the  Peach,  Cherry  and  Plum,  Gum  Traga- 
canth  and  Bassora  Gum,  Agar-Agar  and  the  Mucilages 
of  various  roots,  viz.,  of  mallow  and  comfrey ;  and  of 
certain  seeds,  as  those  of  flax  and  quince. 

Gum  Arabic  exudes  from  the  stems  of  various  species 
of  acacia  that  grow  in  the  tropical  countries  of  the  East, 
especially  in  Arabia  and  Egypt.  It  occurs  in  tear-like, 
transparent,  and,  in  its  purest  form,  colorless  masses. 
These  dissolve  easily  in  their  own  weight  of  water,  form- 
ing a  viscid  liquid,  or  mucilage,  which  is  employed  for 
causing  adhesion  between  surfaces  of  paper,  and  for 
thickening  colors  in  calico-printing. 

Gum  Arabic  is,  however,  commonly  a  mixture  of  at 
least  two  very  similar  gums,  which  are  distinguished  by 
their  opposite  effect  on  polarized  light  and  by  the  differ- 
ent products  which  they  yield  when  boiled  with  dilute 
acids. 

Cherry  Gum. — The  gum  which  frequently  forms 
glassy  masses  on  the  bark  of  cherry,  plum,  apricot,  peach 
and  almond  trees,  is  a  mixture  in  variable  proportions  of 
two  gums,  one  of  which  is  apparently  the  same  as  occurs 
in  gum  arabic,  and  is  fully  dissolved  in  cold  water,  while 
the  other  remains  undissolved,  but 
Bwollen  to  a  pasty  mass  or  jelly. 

Gum  Tragacanth,  which  comes 
to  us  from  Persia  and  Siberia,  has 
much  similarity  in  its  properties 
to  the  insoluble  part  of  cherry 
gum,  as  it  dissolves  but  slightly  in  d '  ""JC/ JC^ 
water  and  swells  up  to  a  paste  or 
jelly. 

The  so-called  Vegetable  mucilages 
much  resemble  the  insoluble  part 
of  cherry  gum  and  are  found  in 
the  seeds  of  flax,  quince,  lemon,  and  in  various  parts  of 
many  plants. 


THE   VOLATILE   PABT  OF  PLANTS.  59 

Flax-seed  mucilage  is  procured  by  soaking  unbroken  flaxseed  in  cold 
water,  with  frequent  agitation,  heating  the  liquid  to  boiling,  strain- 
ing, and  evaporating,  until  addition  of  alcohol  separates  tenacious 
threads  from  it.  It  is  then  precipitated  by  alcohol  containing  a  little 
hydrochloric  acid,  and  washed  by  the  same  mixture.  On  drying,  it 
forms  a  horny,  colorless,  and  friable  mass.  Fig.  13  represents  a  highly 
magnified  section  of  the  ripe  flaxseed.  The  external  cells,  a,  contain 
the  dry  mucilage.  When  soaked  in  water,  the  mucilage  swells,  bursts 
the  cells,  and  exudes. 

The  Pectin  Bodies. — The  flesh  of  beets,  turnips,  and 
similar  roots,  and  of  most  unripe  fruits,  as  apples, 
peaches,  plums,  and  berries  of  various  kinds,  contain  one 
or  several  bodies  which  are  totally  insoluble  in  water,  but 
which,  under  the  action  of  weak  acids  or  alkaline  solu- 
tions, become  soluble  and  yield  substances  having  gummy 
l»r  gelatinous  characters,  that  have  been  described  under 
the  names  pectir*,  pectic  acid,  pectosic  acid,  mctapectic 
acid,  etc.  Their  true  composition  is,  for  the  most  part, 
not  positively  established.  They  are,  however,  closely 
related  to  the  gums.  The  insoluble  substance  thus  trans- 
formed into  gum-like  bodies,  Fremy  termed  pectose. 

The  gums,  as  they  occur  naturally,  are  mostly  mix- 
tures. By  boiling  with  dilute  sulphuric  or  hydrochloric 
acid  they  are  transformed  into  sugars. 

In  the  present  state  of  knowledge  it  appears  probable 
that  the  common  gums,  for  the  most  part,  consist  of  a 
few  chemically  distinct  bodies,  some  of  which  have  been 
distinguished  more  or  less  explicitly  by  such  names  as 
Arabin,  Metarabin,  Pararabin,  Galactin,  Paragalactin, 
etc. 

Arabin,  or  Arabic  Acid,  is  obtained  from  some  va- 
rieties of  Gum  Arabic*  by  mixing  their  aqueous  solution, 
with  acetic  acid  and  alcohol.  It  is  best  prepared  from 
sugar-beet  pulp,  out  of  which  the  juice  has  been  ex- 
pressed, by  heating  with  milk  of  lime ;  the  pulp  is 
thereby  broken  down,  and  to  a  large  extent  dissolves. 


*  Those  sorts  of  commercial  Gum  Arabic  which  deviate  the  plane  of 
polarization  of  light  to  the  left  contain  arabiii  in  largest  proportion.. 


60  HOW  CROPS   GROW. 

The  liquid,  after  separating  excess  of  lime  and  adding 
acetic  acid,  is  mixed  with  alcohol,  whereupon  arabin  is 
precipitated.  Arabin,  thus  prepared,  is  a  milk-white 
mass  which,  while  still  moist,  readily  dissolves  in  water 
to  a  mucilage.  It  strongly  reddens  blue  litmus  and  ex- 
pels carbonic  acid  from  carbonates.  "When  dried  at  212° 
arabin  becomes  transparent  and  has  the  composition 
C12H220ii.  Dried  at  230°  it  becomes  (by  loss  of  a  mole- 
cule of  water)  Ci2H2o010,  or  2  C6H1005. 

Arabin  forms  compounds  with  various  metals.  Those 
with  an  alkali,  lime,  or  magnesia  as  base  are  soluble  iu 
water.  Gum  arabic,  when  burned,  leaves  3  to  4  per  cent 
of  ash,  chiefly  carbonates  of  potassium,  calcium  and  mag- 
nesium. Arabic  acid,  obtained  by  Fremy  from  beets  by 
the  foregoing  method,  but  not  in  a  state  of  purity,  was 
described  by  bim  as  "metapectic  acid."  To  Scheibler 
we  owe  the  proof  of  its  identity  with  the  arabin  of  gum 
arabic. 

Metarabin. — When  arabin  is  dried  and  kept  at  212° 
for  some  time,  it  becomes  a  transparent  mass  which  is  no 
longer  freely  soluble  in  water,  but  in  contact  therewith 
swells  up  to  a  gelatinous  mass.  This  is  designated 
metarabin  by  Scheibler.  It  is  dissolved  by  alkalies,  and 
thus  converted  into  arabates,  from  which  arabin  may  be 
again  obtained. 

The  body  named  pararabin  by  Reichardt,  obtained 
from  beet  and  carrot  pulp  by  treatment  with  dilute  hy- 
drochloric acid,  is  related  to  or  the  same  as  metarabin. 
Fremy's  "pectin,"  obtained  by  similar  treatment  from 
beets,  is  probably  impure  metarabin. 

EXP.  34.— Reduce  several  white  turnips  or  beets  to  pulp  by  grating. 
Inclose  the  pulp  in  a  piece  of  muslin,  and  wash  by  squeezing  in  water 
until  all  soluble  matters  are  removed,  or  until  the  water  comes  oft 
nearly  tasteless.  Bring  the  washed  pulp  into  a  glass  vessel,  with 
enough  dilute  hydrochloric  acid(l  part  by  bulk  of  commercial  muriatic 
acid  to  15  parts  of  water)  to  saturate  the  mass,  and  let  it  stand  48  hours. 
Squeeze  the  acid  liquid,  filter  it,  and  add  alcohol,  when  "  pectin  "  will 


THE  VOLATILE  PART  OF  PLANTS.  61 

It  may  be  that  metarabin  is  identical  with  the  "pec- 
tose  "  of  the  sugar  beet,  since  both  yield  arabin  under  the 
influence  of  alkalies.  It  is  evident  that  the  composition 
found  for  dried  arabin  properly  belongs  to  metarabin,  and 
it  is  probable  that  arabin  consists  of  metarabin  C12H220U 
plus  one  or  several  molecules  of  water,  and  that  metara- 
bin is  an  anhydride  of  arabin. 

Arabin  and  metarabin,  when  heated  with  dilute  sul- 
phuric acid,  are  converted  into  a  cry stalli 'able  sugar 
called  arabinose,  C5H1005.  The  gums  that  exude  from 
the  stems  of  cherry,  plum  and  peach  trees  appear  to  con- 
sist chiefly  of  a  mixture  of  freely  soluble  arabates  with 
insoluble  metarabin.  Gum  Tragacanth  is  perhaps  mostly 
metarabin.  All  these  gums  yield,  by  the  action  of  hot 
dilute  acids,  the  sugar  arabinose. 

Galactin,  C6H1005,  discovered  by  Miiutz  in  the  seeds 
of  alfalfa  and  found  in  other  legumes,  has  the  appearance, 
solubility  in  water  and  general  properties  of  arabin,  and 
is  probably  the  right-polarizing  ingredient  of  gum  arabic. 
Boiled  with  dilute  acids  it  is  converted  into  the  sugar 
galactose,  C6H1206. 

Paragalactin,  C6H1005. — In  the  seeds  of  the  yellow 
lupin  exists  up  to  20  per  cent  of  a  body  that  is  insoluble 
in  water,  but  dissolves  by  warming  with  alkali  solutions, 
and  when  heated  with  dilute  acids  yields  galactose.  Ac- 
cording to  Steiger  it  probably  has  the  composition  CGH1005. 
Maxwell  has  shown  it  to  exist  in  other  leguminous  seeds, 
viz.,  the  pea,  horse-bean  (Faba  vulgaris)  and  vetch. 

In  the  "  Chinese  moss,"  an  article  of  food  prepared  in 
China  from  sea-weeds,  and  in  the  similar  gum  agar  or 
"vegetable  gelatine"  of  Japan,  exists  a  substance  which 
is  insoluble  in  cold  water,  but  with  that  liquid  swells  up 
to  a  bulky  jelly,  and  yields  galactose  when  heated  with 
dilute  acids.  This  corresponds  to  metarabin. 

Xylin,  or  'Wood  Gum. — The  wood  of  many  decidu- 
ous trees,  the  vegetable  ivory  nut,  the  cob  of  Indian 


62  HOW  CEOPS  GROW. 

corn  and  barley  husks,  contain  6  to  20  per  cent  of  a  sub« 
stance  insoluble  in  cold  water,  but  readily  taken  up  in 
cold  solution  of  caustic  soda.  On  adding  to  the  solution 
an  acid,  and  afterwards  alcohol,  a  bulky  white  substance 
separates,  which  may  be  obtained  dry  as  a  white  powder 
or  a  translucent  gum-like  mass.  It  dissolves  very  slightly 
in  boiling  water,  yielding  an  opalescent  solution.  The 
composition  of  this  substance  was  found  by  Thomsen  to 
be  C6H1006. 

Xylin  differs  from  pararabin  and  pectose  in  not  being 
soluble  in  milk  of  lime.  It  is  converted  by  boiling  with 
dilute  sulphuric  acid  into  a  crystallizable  sugar,  xylose, 
whose  properties  have  been  but  little  investigated. 

Flax-seed  Mucilage,  C6H1005,  resembles  metarabin, 
but  by  action  of  hot  dilute  acids  is  resolved  into  cellulose 
and  a  gum,  which  latter  is  further  transformed  into  dex- 
trose. The  yield  of  cellulose  is  about  four  per  cent. 

Quince-Seed  Mucilage  appears  to  be  a  compound  of 
cellulose  and  a  body  like  arabin.  On  boiling  with  dilute 
sulphuric  acid  it  yields  nearly  one-third  its  weight  of  cel- 
lulose, together  with  a  soluble  gum  and  a  sugar,  the  last 
being  a  result  "of  the  alteration  of  the  gum.  The  sugar 
is  similar  to  arabinose. 

The  Soluble  Gums  in  Bread-grains. — In  the  bread- 
tains,  freely  soluble  gums  occur  often  in  considerable 
_roportion. 

ftVBLE  OF  THE  PROPORTIONS  (percent.)  OF  GUM*  IN  VARIOUS  AIR-DRY 
GRAINS  OR  MILL  PRODUCTS. 

(According  to  Von  Jlibra,  Die  Getreidearten  und  das  Brod.) 
Wheat  kernel 4.50     Barley  flour 6.33 


Wheat  flour,  superfine 6.25 

Spelt  flour  ( Triticum  spclta) ..    2.48 

Wheat  bran 8.85 

Spelt  bran 12.52 

Rye  kernel 4.10 

Rye  flour 7.25 

Rye  bran 10.40 


Barley  bran 6.88 

Oat  meal 3.50 

Rice  flour 2.00 

Millet  flour 10.60 

Maize  meal 3.05 

Buckwheat  flour 2.85 


*  The  "  gum  "  in  the  above  table  (which  dates  from  1859),  includes  per- 
haps soluble  starch  and  dextrin  in  some,  if  not  all  cases,  and,  accord- 
ing to  O'Sullivan,  barley,  wheat  and  rye  contain  two  distinct  left-pol- 
arizing gums,  which  he  lerms  a-atnylan  and  b-amylctn.  These  occur  in 
barley  to  the  extent  of  2.3  per  cent.  By  action  of  acids  they  yield 
dextrose. 


THE  VOLATILE  PART  OF  PLANTS.         63 

The  experiments  of  Grouven  show  that  gum  arable  is 
digestible  by  domestic  animals.  There  is  little  reason  to 
doubt  that  all  the  gums  are  digestible  and  serviceable  as 
ingredients  of  the  food  of  animals. 

#.  The  Glucoses,  C6Hi206  (or  C5H1005),  are  a  class  of 
sugars  having  similar  or  identical  composition,  but  dif- 
fering from  each  other  in  solubility,  sweetness,  melting 
point,  crystal-form  and  action  on  polarized  light. 

The  glucoses,  with  one  exception,  contain  in  100  parts  : 

Carbon  ...........................  40.00 

Hydrogen  ........................    6.67 

Oxygen  ...........................  53.33 

100.00 

Levulose,  or  Fruit  Sugar  (Fructose),  C«Hi20«, 
exists  mixed  with  other  sugars  in  sweet  fruits,  honey  and 
molasses.  Inulin  and  levulin  are  converted  into  this 
sugar  by  long  boiling  with  dilute  acids,  or  with  water 
alone.  When  pure,  it  forms  colorless  crystals,  which 
melt  at  203°,  but  is  usually  obtained  as  a  syrup.  Its 
sweetness  is  equal  to  that  of  saccharose. 

Dextrose  or  Grape  Sugar,  C6H1206,  naturally  oc- 
curs associated  with  levulose  in  the  juices  of  plants  and 
in  honey.  Granules  of  dextrose  separate  from  the  juice 
of  the  grape  on  drying,  as  may  be  seen  in  old  "  candied  " 
raisins.  Honey  often  granulates,  or  candies,  on  long 
keeping,  from  the  crystallization  of  its  dextrose. 

Dextrose  is  formed  from  starch  and  dextrin  by  the  ac- 
tion of  hot  dilute  acids,  in  the  same  way  that  levulose  is 
produced  from  inulin.  In  the  pure  state  it  exists  as 
minute,  colorless  crystals,  and  is,  weight  for  weight,  but 
two-thirds  as  sweet  as  saccharose  or  cane-sugar.  It  fuses 
at  295°. 


Dextrose  unites  chemically  to  water.  Hydrated  glucose,  Cs 
occurs  in  commerce  in  an  impure  state  as  a  crystalline  mass,  which 
becomes  doughy  at  a  slightly  elevated  temperature.  This  hydrate 
loses  its  crystal-water  at  212°. 

Dissolved  in  water,  dextrose  yields  a  syrup,  which  is 


64  HOW  CEOPS  GROW. 

thin,  and  destitute  of  the  ropiness  of  cane-sugar  syrup. 
It  does  not  crystallize  (granulate)  so  readily  as  cane- 
sugar. 

EXP.  30. — Mix  100  c.  c.  of  water  with  30  drops  of  strong  sulphuric  acid, 
and  heat  to  vigorous  boiling  in  a  glass  flask.  Stir  10  grains  of  starch 
with  a  little  water,  and  pour  the  mixture  into  the  hot  liquid,  drop  by 
drop,  so  as  not  to  interrupt  the  boiling.  The  starch  dissolves,  and  passes 
successively  into  amiduliii,  dextrin,  and  dextrose.  Continue  the  ebul- 
lition for  several  hours,  replacing  the  evaporated  water  from  time  to 
time.  To  remove  the  sulphuric  acid,  add  to  the  liquid,  which  may  be 
still  milky  from  impurities  in  the  starch,  powdered  chalk,  until  the  sour 
taste  disappears;  filter  from  the  calcium  sulphate  (gypsum)  that  is 
formed,  and  evaporate  the  solution  of  dextrose*  at  a  gentle  heat  to  a 
syrupy  consistence.  On  long  standing  it  may  crystallize  or  granulate. 

By  this  method  is  prepared  the  so-called  grape-sugar,  or  starch-sugar 
of  commerce,  which  is  added  to  grape-juice  for  making  a  stronger 
wine,  and  is  also  employed  for  preparing  syrups  and  imitating  molasses. 
The  syrups  thus  made  from  starch  or  corn  are  known  in  the  trade  as 
glucose.^  Imitation-molasses  is  a  mixture  of  dextrose-syrup  with  some 
dextrin  to  make  it  "  ropy." 

Even  cellulose  is  convertible  into  dextrose  by  the  pro- 
longed action  of  hot  acids.  If  paper  or  cotton  be  first 
dissolved  in  strong  sulphuric  acid,  and  the  solution 
diluted  with  water  and  boiled,  the  cellulose  is  readily 
transformed  into  dextrose.  Sawdust  has  thus  been  made 
to  yield  an  impure  syrup,  suitable  for  the  production  of 
alcohol. 

In  the  formation  of  dextrose  from  cellulose,  starch,  amidulin  and 
dextrin,  the  latter  substances  take  up  the  elements  of  water  as  repre- 
sented by  the  equation 

Starch,  etc.  Water.  Glucose. 

CeH10O5  +  H2O  =  C6H12O6 

In  this  process,  90  parts  of  starch,  etc.,  yield  100  parts  of  dextrose. 

Trommer's  Copper  test. — A  characteristic  test  for  dextrose  and  levu- 
lose  is  found  in  their  deportment  towards  an  alkaline  solution  of  cop- 
per, which  readily  yields  up  oxygen  to  these  sugars,  the  copper  being 
reduced  to  yellow  cuprous  hydroxide  or  red  cuprous  oxide. 

EXP.  31.— Prepare  the  copper  test  by  dissolving  together  in  30  c.  e.  of 
warm  water  a  pinch  of  sulphate  of  copper  and  one  of  tartaric  acid: 
add  to  the  liquid,  solution  of  caustic  potash  until  it  acquires  a  slip. 


*  If  the  boiling  has  been  kept  up  but  an  hour  or  so,  the  dextrose  will 
contain  dextrin,  as  may  be  ascertained  by  mixing  a  small  portion  of 
the  still  acid  liquid  with  5  times  its  bulk  of  strong  alcohol,  which  will 
precipitate  dextrin,  but  not  dextrose. 

t  Under  the  name  glucose,  the  three  sugars  levulose,  dextrose  and 
maltose  were  formerly  confounded  together,  by  chemists. 


THE  VOLATILE  PART  OF  PLANTS.  65 

pcry  feel.  Place  in  separate  test  tubes  a  few  drops  of  solution  of  cane- 
sugar,  a  similar  amount  of  the  dextrin  solution,  obtained  in  Exp.  28; 
of  solution  of  dextrose,  from  raisins,  or  from  Exp.  30;  and  of  molasses  ; 
add  to  each  a  little  of  the  copper  solution,  and  place  them  in  a  vessel 
of  hot  water.  Observe  that  the  saccharose  and  dextrin  suffer  little  or 
no  alteration  for  a  long  time,  while  the  dextrose  and  molasses  shortly 
cause  the  separation  of  cuprous  oxide. 

EXP.  32.— Heat  to  boiling  a  little  white  cane-sugar  with  30  c.  c.  of 
water,  and  3  drops  of  strong  sulphuric  acid,  in  a  glass  or  porcelain  dish, 
for  15  minutes,  supplying  the  waste  of  water  as  needful,  and  test  the 
liquid  as  in  the  last  Exp.  This  treatment  transforms  saccharose  into 
dextrose  and  levulose. 

The  quantitative  estimation  of  the  sugars  and  of  starch  is  commonly 
based  upon  the  reaction  just  described.  For  this  purpose  the  alkaline 
copper  solution  is  made  of  a  known  strength  by  dissolving  a  given 
weight  of  sulphate  of  copper,  etc.,  in  a  given  volume  of  water,  and  tha 
dextrose  or  levulose,  or  a  mixture  of  both,  being  likewise  made  to  a 
known  volume  of  solution,  the  latter  is  allowed  to  flow  slowly  from  a 
graduated  tube  into  a  measured  portion  of  warm  copper  solution,  until 
the  blue  color  is  discharged.  Saccharose  is  first  converted  into  dex- 
trose and  levulose,  by  heating  with  an  acid,  and  then  examined  in  the 
same  manner. 

Starch  is  transformed  into  dextrose  by  heating  with  hydrochloric 
acid  or  warming  with  saliva.  The  quantity  of  sugar  stands  in  definite 
relation  to  the  amount  of  copper  separated,  when  the  experiment  is 
carried  out  under  certain  conditions.  See  Allihn,  Jour./ilr  Pr.  Chemie, 
XXII,  p.  52, 1880. 

Galactose,  C6H1206,  is  formed  by  treating  right- 
polarizing  gum  arabic,  galactin,  or  milk-sugar  with 
dilute  acids.  It  crystallizes,  is  sweet,  melts  at  289°  and 
with  nitric  acid  yields  mucic  acid  (distinction  from  ara- 
binose,  dextrose  and  levulose). 

Mannose  (Seminose?)  C6H1206  is  a  fermentable  sugar 
prepared  artificially  by  oxidation  of  mannite  (see  p.  74), 
and,  according  to  E.  Fischer,  is  probably  identical  with 
the  Seminose  found  by  Reiss  as  a  product  of  the  action 
of  acids  on  a  body  existing  in  the  seeds  of  coffee  and  in 
palm  nuts.  (Serichte,  XXII,  p.  365). 

Arabinose,  C5Hi005,  obtained  from  arabin  (of  left- 
polarizing  gum  arabic),  and  from  cherry  gum  by  action 
of  hot  dilute  acids,  appears  in  rhombic  crystals.  It  is 
less  sweet  than  cane  sugar,  and  fuses  at  320°. 

c.  The  Sucroses,  C^H^On,  are  sugars  which,  boiled  with 
dilute  acids,  undergo  chemical  change  by  taking  up  the 
5 


66  HOW  CROPS  GAOW. 

elements  of  water  and  are  thereby  resolved  into  glucoses. 
In  this  decomposition  one  molecule  of  sucrose  usually 
yields  either  two  molecules  of  one  glucose  or  a  molecule  each 
of  two  glucoses,  C12H220U  -f  ILO  =  C6H1206  -f  C6H1206. 

Saccharose,  or  Cane  Sugar,  Ci2H22On,  so  called 
because  first  and  chiefly  prepared  from  the 
sugar-cane,  is  the  ordinary  sugar  of  com- 
merce. When  pure,  it  is  a  white  solid, 
readily  soluble  in  water,  forming  a  color-  Fig.  14. 
less,  ropy,  and  intensely  sweet  solution.  It  crystallizes 
in  rhombic  prisms  (Fig.  14),  which  are  usually  small,  as 
in  granulated  sugar,  but  in  the  form  of  rock-candy  may 
be  found  an  inch  or  more  in  length.  The  crystallized 
sugar  obtained  largely  from  the  sugar-beet,  in  Europe, 
and  that  furnished  in  the  United  States  by  the  sugar- 
maple  and  sorghum,  when  pure,  are  identical  with  cane- 
sugar. 

Saccharose  also  exists  in  the  vernal  juices  of  the  wal- 
nut, birch,  and  other  trees.  It  occurs  in  the  stems  of 
unripe  maize,  in  the  nectar  of  flowers,  in  fresh  honey,  in 
parsnips,  turnips,  carrots,  parsley,  sweet  potatoes,  in  the 
stems  and  roots  of  grasses,  in  the  seeds  of  the  pea  and 
bean,  and  in  a  multitude  of  fruits. 

EXP.  29. — Heat  cautiously  a  spoonful  of  white  sugar  until  it  melts  (at 
356°  F.)  to  a  clear  yellow  liquid.  On  rapid  cooling,  it  gives  a  transpar- 
ent mass,  known  as  barley  swjar,  which  is  employed  in  confectionery. 
At  a  higher  heat  it  turns  brown,  froths,  emits  pungent  vapors,  and  be- 
comes burnt  sugar,  or  caramel,  which  is  used  for  coloring  soups,  ale,  etc. 

The  quantity  per  cent  of  saccharose  in  the  juice  of  various  plants  is 
given  in  the  annexed  table.  It  is,  of  course,  variable,  depending  upon 
the  variety  of  plant  in  case  of  cane,  beet,  and  sorghum,  as  well  as  upon 
the  stage  of  growth. 

SACCHAROSE  IN  PLANTS. 

Per  cent. 

Sugar-cane,  average 18   Peligot. 

Sugar-beet,        "       10        " 

Sorghum  13   Collier. 

Maize,  just  flowered 3|  Liidersdorff. 

Sugar-maple,  sap,  average 2i  Liebig. 

Bed  maple,       "          "         2J     " 


THE  VOLATILE  PART  OF  PLANTS.  67 

The  composition  of  saccharose  is  the  same  as  that  of 
arabin,  and  it  contains  in  100  parts  : 

Carbon 42.11 

Hydrogen 6.43 

Oxygen 51.46 

100.00 

Cane-sugar,  by  long  boiling  of  its  concentrated  aqueous 
solution,  and  under  the  influence  of  hot  dilute  acids  (Exp. 
32)  and  yeast,  loses  its  property  of  ready  crystallization, 
and  is  converted  into  levulose  and  dextrose. 

According  to  Dubrunfaut,  a  molecule  of  cane-sugar  takes  up  the  ele- 
ments of  a  moleciile  (5.26  per  cent.)  of  water,  yielding  a  mixture  of 
equal  parts  of  levulose  and  dextrose.  This  change  is  expressed  in 
chemical  symbols  as  follows  : 

Cl2H22On     +    H,0    =     C8H1206     +     C6H1206 
Cane-sugar.      Water.       Levulose.         Dextrose. 

This  alterability  on  heating  its  solutions  occasions  a 
loss  of  one-third  to  one-half  of  the  saccharose  that  is 
really  contained  in  cane-juice,  when  this  is  evaporated  in 
open  pans,  and  is  one  reason  why  solid  sugar  is  obtained 
from  the  sorghum  in  open-pan  evaporation  with  such  dif- 
ficulty. 

Molasses,  sorghum  syrup,  and  honey  usually  contain 
all  three  of  these  sugars. 

Honey-dew,  that  sometimes  falls  in  viscid  drops  from 
the  leaves  of  the  lime  and  other  trees,  is  essentially  a  mix- 
ture of  the  three  sugars  with  some  gum.  The  mannas  of 
Syria  and  Kurdistan  are  of  similar  composition. 

Maltose,  C12H22011.H20,  is  formed  in  the  sprouting 
of  seeds  by  the  action  of  a  ferment,  called  diastase,  on 
starch.  It  is  also  prepared  by  treating  starch  or  glycogen 
with  saliva.  In  either  case  the  starch  (or  glycogen)  takes 
up  the  elements  of  water,  2  C6H1005  -j-  H20  =  C12H22On. 
Maltose  in  crystallizing  unites  with  another  molecule  of 
water,  which  it  loses  at  212°.  Maltose,  thus  dried, 
attracts  moisture  with  great  avidity. 

Boiled  with  dilute  acids  one  molecule  of  maltose  yields 


68  '  SOW  CEOPS  GROW. 

two  molecules  of  dextrose,  Ci2H22On  -j-  n20  =  2  C6H1206. 
Maltose  is  also  produced  when  starch  and  dextrin  are 
heated  with  dilute  acids,  and  thus  appears  to  be  an  inter- 
mediate stage  of  their  transformation  into  dextrose. 

Maltose  is  accordingly  an  ingredient  of  some  commer- 
cial "grape-sugars"  made  from  starch  by  boiling  with 
diluted  sulphuric  acid. 

Lactose,  or  Milk  Sugar,  Ci2H22Oii  -}-  H20,  is  the 
sweet  principle  of  the  milk  of  animals.  It  is  prepared 
for  commerce  by  evaporating  whey  (milk  from  which 
casein  and  fat  have  been  separated  for  making  cheese). 
In  a  state  of  purity  it  forms  transparent,  colorless  crys- 
tals, which  crackle  under  the  teeth,  and  are  but  slightly 
sweet  to  the  taste.  When  dissolved  to  saturation  in 
water,  it  forms  a  sweet  but  thin  syrup.  Heated  to  290° 
the  crystals  become  water-free. 

Lactose  is  said  to  occur  with  cane-sugar  in  the  sapo- 
dilla  (fruit  of  Acliras  sapotd)  of  tropical  countries. 
Treatment  with  dilute  sulphuric  acid  converts  it  into 
galactose  and  dextrose. 

C12H22On     +    H2O     =     C6H12O6      +     C6H12O6 
Lactose.          Water.        Galactose.         Dextrose. 

Raffinose,  C18H32016  -f-  5  H20  (?),  first  discovered 
by  Loiseau  in  beet-sugar  molasses,  was  afterwards  found 
by  Berthelot  in  eucalyptus  manna,  by  Lippmann  in  beet- 
root, and  by  Boehm  &  Ritthausen  in  cotton-seed.  It 
crystallizes  in  fine  needles,  and  is  but  slightly  sweet.  It 
begins  to  melt  at  190°  with  loss  of  crystal-water,  which 
may  be  completely  expelled  at  212°.  The  anhydrous 
sugar  fuses  at  236°.  It  is  more  soluble  in  water  and  has 
higher  dextrorotatory  power  than  cane-sugar.  Heated 
with  dilute  acids  it  yields  dextrose,  levulose  and  galactose. 

C18H320)8  +  2  H20  =  3  (C6H1206). 

The  Sugars  in  Bread- Grains. — The  older  observers 
assumed  the  presence  of  dextrose  in  the  bread-grains. 


THE  VOLATILE  PART  OF  PLANTS.  69 

Thus,  Vauquelin  found,  or  thought  he  found,  8.5%  of 
this  sugar  in  Odessa  wheat.  More  recently,  Peligot, 
Mitscherlich,  and  Stein  denied  the  presence  of  any  sugar 
in  these  grains.  In  his  work  on  the  Cereals  and  Bread, 
(Die  Getreidearten  und  das  Brod,  1860,  p.  163),  Von 
Bibra  reinvestigated  this  question,  and  found  in  fresh- 
ground  wheat,  etc.,  a  sugar  having  some  of  the  charac- 
ters of  saccharose,  and  others  of  dextrose  and  levulose. 
Marcker  and  Kobus,  in  1882,  report  maltose  (which  was 
unknown  to  the  earlier  observers)  in  sound  barley,  and 
maltose  and  dextrose  in  sprouted  barley. 

Von  Bibra  found  in  the  flour  of  various  grains  the  following  quanti- 
ties of  sugar : 

PROPORTIONS  OF  SUGAR  IN  AIR-DRY  FLOUR,  BRAN,  AND  MEAL. 

Per  cent. 

Wheat  flour 2.33 

Spelt  flour 1.41 

Wheat  bran 4.30 

Spelt  bran 2.70 

Rye  flour 3.46 

Rye  bran 1.86 

Barley  meal 3.04 

Barley  bran 1.90 

Oat  meal 2.19 

Rice  flour 0.39 

Millet  flour 1.30 

Maize  meal 3.71 

Buckwheat  meal 0.91 

Olucosides. — There  occur  in  the  vegetable  kingdom  a 
large  number  of  bodies,  usually  bitter  in  taste,  which 
contain  dextrose,  or  a  similar  sugar,  chemically  combined 
with  other  substances,  or  that  yield  it  on  decomposition. 
Salicin,  from  willow  bark  ;  phloridzin,  from  the  bark  of 
the  apple-tree  root ;  jalapin,  from  jalap  ;  aesculin,  from 
the  horse-chestnut,  and  amygdalin,  in  seeds  of  almond, 
peach,  plum,  apple,  cherry,  and  in  cherry-laurel  leaves, 
are  of  this  kind.  The  sugar  may  be  obtained  from  these 
so-called  glucosides  by  heating  with  dilute  acids. 

The  seeds  of  mustard  contain  the  glucoside  myronic  acid  united  to 
potassium.  This,  when  the  crushed  seeds  are  wet  with  water,  breaks 
up  into  dextrose,  mustard-oil,  and  acid  potassium  sulphate,  as  follows : 
C10  H18  K  N  S,  010  =  C6HI208  +  C3  H6  N  C  S  +  K  H  S  O« 

Xhe  cambial  juice  of  the  conifers  contains  conifer  in,  crystallizing  in 


70  HOW  CHOPS  GROW. 

brilliant  needles,  which  yields  dextrose  and  a  resin  by  action  of  dilute 
acid,  and  by  oxidation  produces  vanillin,  the  flavoring  principle  of  the 
vanilla  bean. 

Mutual  Transformations  of  the  Carbhydrates. — One  of 
the  most  remarkable  facts  in  the  history  of  this  group  of 
bodies  is  the  facility  with  which  its  members  undergo 
mutual  conversion.  Some  of  these  changes  have  been 
already  noticed,  but  we  may  appropriately  review  them 
here. 

a.  Transformations  in  the  plant.  — In  germinati  on,  the 
starch  which  is  largely  contained  in  seeds  is  converted 
into  amidulin,  dextrin,  maltose  and  dextrose.  It  thus  ac- 
quires solubility,  and  passes  into  the  embryo  to  feed  the 
young  plant.  Here  these  are  again  solidified  as  cellulose, 
starch,  or  other  organic  principle,  yielding,  in  fact,  the 
chief  part  of  the  materials  for  the  structure  of  the  seed- 
ling. 

At  spring-time,  in  cold  climates,  the  starch  stored  up 
over  winter  in  the  new  wood  of  many  trees,  especially  the 
maple,  appears  to  be  converted  into  the  sugar  which  is 
found  so  abundantly  in  the  sap,  and  this  sugar,  carried 
upwards  to  the  buds,  nourishes  the  young  leaves,  and  is 
there  transformed  into  cellulose,  and  into  starch  again. 

The  sugar-beet  root,  when  healthy,  yields  a  juice  con- 
taining 10  to  14  per  cent,  of  saccharose,  and  is  destitute 
of  starch.  Schacht  has  observed  that,  in  a  certain  dis- 
eased state  of  the  beet,  its  sugar  is  partially  converted 
into  starch,  grains  of  this  substance  making  their  appear- 
ance. (Wilda's  Centralblatt,  1863,  II,  p.  217.) 

In  some  years  the  sugar-beet  yields  a  large  amount  of 
arabin,  in  others  but  little. 

The  analysis  of  the  cereal  grains  sometimes  reveals  the 
presence  of  dextrin,  at  others  of  sugar  or  gum. 

Thus,  Stepf  found  no  dextrin,  but  both  gum  and  sugar  in  maize-meal 
(Jour,  filr  Prakt.  Chem.,  76,  p.  92);  while  Fresenius,  in  a  more  recent 
analysis  ( Vs.  St.,  I,  p.  180),  obtained  dextrin,  but  neither  sugar  nor  gum. 
The  sample  of  maize  examined  by  Stepf  contained  3.05  p.  c.  gum  and 
3.71  p.  c.  sugar ;  that  analyzed  by  Fresenius  yielded  2.33  p.  «.  dextrin. 


THE  VOLATILE  PART  OF  PLANTS.  71 

Marcker  &  Kobus  made  comparative  analyses  of  well-cured  and  of 
sprouted  barley,  with  the  following  results  per  cent: 

Sound.  Grown. 

Starch 64.10  57.98 

Soluble  starch 1.76  1.17 

Dextrin 1.10  0.00 

Dextrose 0.00  4.92     ' 

Maltose 3.12  7.92 

The  various  gums  are  a  result  of  the  transformation  of 
cellulose,  as  Mohl  first  showed  by  microscopic  study. 

b.  In  the  animal,  the  substances  we  have  been  describ- 
ing also  suffer  transformation  when  employed  as  food. 
During  the  process  of  digestion,  cellulose,  so  far  as  it  is 
acted  upon,  starch,  dextrin,  and  probably  the  gums,  are 
all  converted  into  dextrose  or  other  sugars,  and  from 
these,  in  the  liver  especially,  glycogen  is  formed. 

c.  Many  of  these  changes  may  also  be  produced  apart 
from  physiological  agency,  by  the  action  of  heat,  acids, 
and  ferments,  operating  singly  or  jointly. 

Cellulose  and  starch  are  converted,  by  boiling  with  a 
ililute  acid,  into  amidulin,  dextrin,  maltose  and  dextrose. 
Cellulose  and  starch  acted  upon  for  some  time  by  strong 
nitric  acid  give  compounds  from  which  dextrin  may  be 
separated.  Cellulose  nitrate  sometimes  yields  gum  (dex- 
trin) by  its  spontaneous  decomposition.  A  kind  of  gum 
also  appears  in  solutions  of  cane-sugar  or  in  beet-juice, 
•when  they  ferment  under  certain  conditions.  Inulin  and 
the  gums  yield  glucoses,  but  no  dextrin,  when  boiled 
with  weak  acids. 

d.  It  will  be  noticed  that  while  physical  and  chemical 
agencies  produce  these  metamorphoses  mostly  in  one  di- 
rection, under  the  influence  of  life  they  go  on  in  either 
direction. 

In  the  laboratory  we  can  in  general  only  reduce  from  a 
higher,  organized,  or  more  complex  constitution  to  a 
lower  and  simpler  one.  In  the  vegetable,  however,  all 
these  changes,  take  place  with  the  greatest  facility. 

The  Chemical   Composition  of  the  Carbhydra/tes. — It 


HOW   CROPS   GROW. 


has  already  appeared  that  the  substances  just  described 
stand  very  closely  related  to  each  other  in  chemical  com- 
position. In  the  following  table  their  composition  is  ex- 
pressed in  formulae. 


CHEMICAL 

FORMULA:  OF  THE  CARBHYDBATES. 

Amyloses. 

Dried 

Cellulose, 

C«  H10  O5 

Soluble  cellulose, 
Amyloid, 

} 

C.H1006* 

Starch, 

CB  H,0  O5 

Soluble  starch, 

) 

Amidulin, 

J 

C6  H10  06  * 

Amylodextrin, 

) 

Dextrin, 

C6  H10  05 

Inulin, 

6  (C6  H10  06)  +  H2  0  = 

Cgg  H62  O  31 

Levulin, 

2  (C8  H1()  Og)  -f-  H2  O  ~ 

C12  HJJ  On 

Glycogen, 

Cg  H10  O6 

Pectin, 

(?) 

Arabin,        ) 
Metarabin,  ) 

O  /r1    TT      f\  \    I    TT    f\ 
i,  ^g  ±ljo  \Jg)  -}-  Jlj  \J 

C«  HJJ  O,, 

Galactin, 

C6  H10  05 

Paragalactin, 

C6  H10  05 

Flax-seed  mucilage, 

Cg  H10  Os 

Quince-seed  mucilage, 

C6  H10  05  +  2  (C,  H10  06>-HtO  = 

C18  HM  Ow 

Glucoses. 

Crystallized 

Levulose, 

C6  H12  06 

C6  Ht2  Og 

Dextrose, 

C6  Hu  O7  and  C6  Hu  O6 

C6  H12  06 

Galactose, 

C6  H12  O6 

C6  H12  0, 

Mannose, 

C6H,,06 

CgH12Og 

Arabinose, 

Cg  H10  O6 

Cs  H10  Os 

Sucroses. 

Saccharose, 

Cj2  H^  Ou 

C12HMOn 

Maltose, 

C12  HM  Ou 

C12  H22  Ou 

Lactose, 

C12  HM  O12 

C12  H22  Otl 

Rafflnose, 

C18  H42  O2i 

Cis  HS2  O16 

As  above  formulated,  it  is  seen  that  all  these  bodies, 
except  arabinose,  contain  6  atoms  of  carbon,  or  a  num- 
ber which  is  some  simple  multiple  of  6,  united  to  as  much 
hydrogen  and  oxygen  as  form  in  most  cases  5,  6  or  11 
molecules  of  water  (H20).  Being  thus  composed  of  car- 
bon and  the  elements  of  water  they  are  termed  CarWiy- 
drates. 

The  mutual  convertibility  of  the  carbhydrates  is  the 

*  These  soluble  bodies  when  dried  probably  lose  water  which  is 
essential  U>  their  composition,  as  on  drying  they  become  insoluble. 


THE  VOLATILE  PART  OF   PLANTS.  73 

easier  to  understand  since  it  takes  place  by  the  loss  or 
gain  of  several  molecules  of  water. 

The  formulae  given  are  the  simplest  that  accord  with 
the  results  of  analysis.  In  case  of  many  of  the  amyloses 
it  is  probable  that  the  above  formulae  should  be  multi- 
plied by  2,  4,  or  6,  or  even  more,  in  order  to  reach  the 
true  molecular  weight. 

Isomerism. — Bodies  which — like  cellulose  and  dextrin,  or  like  levu- 
lose  and  dextrose — are  identical  in  composition,  and  yet  are  character- 
ized by  different  properties  and  modes  of  occurrence,  are  termed  isom- 
eric;  they  are  examples  of  isomerism.  These  words  are  of  Greek  deri- 
vation, and  signify  of  equal  measure. 

We  must  suppose  that  the  particles  of  isomeric  bodies  which  are  com- 
posed of  the  same  kinds  of  matter,  and  in  the  same  quantities,  exist  in 
different  states  of  arrangement.  The  mason  can  build,  from  a  given 
number  of  bricks  and  a  certain  amount  of  mortar,  a  simple  wall,  an 
aqueduct,  a  bridge  or  a  castle.  The  composition  of  these  unlike  struc- 
tures may  be  the  same,  both  in  kind  and  quantity ;  but  the  structures 
themselves  differ  immensely,  from  the  fact  of  the  diverse  arrangement 
of  their  materials.  In  the  same  manner  we  may  suppose  starch  to  dif- 
fer from  dextrin  by  a  difference  in  the  relative  positions  of  the  atoms 
of  carbon,  hydrogen,  and  oxygen  in  the  molecules  which  compose 
them. 

By  use  of  "  structural  formulae  "  it  is  sought  to  represent  the  different 
arrangement  of  atoms  in  the  molecules  of  isomeric  bodies.  In  case 
of  substances  so  complex  as  the  sugars,  attempts  of  this  kind  have  but 
recently  met  with  success.  The  following  formulae  exhibit  to  the 
chemist  the  probable  differences  of  constitution  between  dextrose  and 
levulose. 

Dextrose.  Levulose. 

H  H 

H— C— O  H  H— C— O  H 
H— C— O  H                                               C— O 

C-H  H-C-0  H 

H— C— O  H  H    C— O  H 

H— C— O  H  H    C— O  H 

_  C— O  H  H    C— O  H 
i                                                        i 

To  those  familiar  with  advanced  Organic  Chemistry  the  foregoing 
formulae,  to  some  extent,  "account  for"  the  chemical  characters  of 
these  sugars,  and  explain  the  different  products  which  they  yield 
under  decomposing  influences. 

APPENDIX  TO  THE  CARBHYDRATES. 

Nearly  related  to  the  Carbhydrates  are  the  following  suostances :— 


74  HOW   CROPS  GROW. 


Mannite,  C6HMO6,  is  abundant  in  the  so-called  manna  of  the  apoth- 
ecary which  exudes  from  the  bark  of  several  species  of  ash  that 
grow  in  the  eastern  hemisphere  (Ji'raxinus  ornus  and  rotund  ij'olia).  It 
likewise  exists  in  the  sap  of  our  fruit  trees,  in  edible  mushrooms,  and 
sometimes  is  formed  in  the  fermentation  of  sugar  (viscous  fermenta- 
tion). It  appears  in  minute  colorless  crystals  and  has  a  sweetish  taste. 
It  may  be  obtained  from  dextrose  and  levulose  by  the  action  of 
nascent  hydrogen  as  liberated  from  sodium  amalgam  and  water, 
C6H12O6  +  H2  =  C6H14O6. 

Dulcite,  CftHuOg,  is  a  crystalline  substance  found  in  the  common  cow- 
wheat  (Melampyrum  nemorostim)  and  in  Madagascar  manna.  It  is 
obtained  from  milk-sugar  by  the  action  of  sodium  amalgam. 

The  isomeres  mannite  and  dulcite,  when  acted  on  by  nitric  acid,  are 
converted  into  acids  which  are  also  isomeric.  Mannite  yields  saccharic 
acid,  which  is  also  formed  by  treating  cane-sugar,  dextrose,  levulose, 
dextrin  and  starch  with  nitric  acid.  Dulcite  yields,  by  the  same  treat- 
ment, mucic  acid,  which  is  likewise  obtained  from  arabin  and  other 
gums.  Milk-sugar  yields  both  saccharic  and  mucic  acid.  Saccharic 
acid  is  very  soluble  in  water.  Mucic  acid  is  quite  insoluble.  Both 
have  the  formula  C6Hj0O8. 

The  Pectin-bodies.  The  juice  of  many  ripe  fruits,  when  mixed  with 
alcohol,  yields  a  jelly-like  precipitate  which  has  long  been  known 
under  the  name  of  pectin.  "When  the  firm  flesh  of  acid  winter-fruits  is 
subjected  to  heat,  as  in  baking  or  stewing,  it  sooner  or  later  softens, 
becomes  soluble  in  water  and  yields  a  gummy  liquid  from  which  by 
adding  alcohol  the  same  or  a  similar  gelatinous  substance  is  separated. 
Fremy  supposes  that  in  the  pulp  "  pectose  "  exists  which  is  transformed 
by  acids  and  heat  into  pectin. 

Exp.  33. — Express,  and,  if  turbid,  filter  through  muslin  the  juice  of  a 
ripe  apple,  pear,  or  peach.  Add  to  the  clear  liquid  its  own  bulk  of 
alcohol.  Pectin  is  precipitated  as  a  stringy,  gelatinous  mass,  which, 
on  drying,  shrinks  greatly  in  bulk,  and  forms,  if  pure,  a  white  sub- 
stance that  may  be  easily  reduced  to  powder,  and  is  readily  soluble  in 
told  water. 

Pectosic  and  Pectic  Acids.  These  bodies,  according  to  Fremy,  com- 
pose the  well-known  fruit-jellies.  They  are  both  insoluble  or  nearly 
80  in  cold  water,  and  remain  suspended  in  it  as  a  gelatinous  mass. 
Pectosic  acid  is  soluble  in  hot  water,  and  is  supposed  to  exist  in  those 
fruit-jellies  which  liquefy  on  heating  but  gelatinize  on  cooling.  Pec- 
tic  acid  is  stated  to  be  insoluble  in  hot  water.  According  to  Fremy, 
pectin  is  changed  into  pectosic  and  pectic  acids  and  finally  into  meta- 
pectic  acid  by  the  action  of  heat  and  during  the  ripening  process. 

EXP.  35. — Stew  a  handful  of  sound  cranberries,  covered  with  water, 
just  long  enough  to  make  them  soft.  Observe  the  speedy  solution  of 
the  firm  pulp  or  "pectose."  Strain  through  muslin.  The  juice  contains 
soluble  pectin,  which  may  be  precipitated  from  a  small  portion  by 
alcohol.  Keep  the  remaining  juice  heated  to  near  the  boiling  point  in 
a  water  bath  (i.  e.,  by  immersing  the  vessel  containing  it  in  a  larger 
one  of  boiling  water).  Alter  a  time,  which  is  variable  according  to 
the  condition  of  the  fruit,  and  must  be  ascertained  by  trial,  the  juice 
on  cooling  or  standing  solidifies  to  a  jelly,  that  dissolves  on  warming, 
and  reappears  again  on  cooling — Fremy's  pectosic  acid.  By  further 


THE  VOLATILE   PART   OF   PLANTS.  75 

heating,  the  juice  may  form  a  jelly  which  is  permanent  when  hot — 
pectic  acid. 

Other  ripe  fruits,  as  quinces,  strawberries,  peaches,  grapes,  apples, 
etc.,  may  be  employed  for  this  experiment,  but  in  any  case  the  time 
required  for  the  juice  to  run  through  these  changes  cannot  be  pre- 
dicted safely,  and  the  student  may  easily  fail  in  attempting  to  fol- 
low them. 

Scheibler  having  shown  that  Fremy's  metapectic  acid  of  beets  is 
arable-  acid,  it  is  probable  that  Fremy's  pectin,  pectic  acid  and  pectosic 
acid  of  fruits,  are  bodies  similar  to  or  identical  witli  the  gums*  already 
described.  The  pectin  bodies  of  fruits  have  not  yet  been  certainly  ob- 
tained in  a  state  of  purity,  since  the  analyses  of  preparations  by  vari- 
ous chemists  do  not  closely  agree. 

The  Vegetable  Acids. — Nearly  every  family  of  the 
vegetable  kingdom,  so  far  as  investigated,  contains  one 
or  more  organic  acids  peculiar  to  itself.  Those  of  more 
general  occurrence  which  alone  concern  us  here  are  few 
in  number  and  must  be  noticed  very  concisely. 

The  vegetable  acids  rarely  occur  in  plants  in  the  free 
state,  but  are  for  the  most  part  united  to  metals  or 
to  organic  bases  in  the  form  of  salts.  The  vegetable 
acids  consist  of  carboxyl,  COOH,  united  generally  to 
a  hydrocarbon  group.  They  are  monobasic,  dibasic  or 
tribasic,  according  as  they  contain  one,  two  or  three 
carboxyls. 

The  Monobasic  Acids,  to  be  mentioned  here,  fall  into 
two  groups,  viz. :  Fatty  acids  and  Oxyfatty  acids. 

THE  FATTY  ACIDS  constitute  a  remarkable  "homolo- 
gous series, "  the  names  and  formulae  of  a  number  of 
which  are  here  given : 

Found  in 

Formic       acid,  H,  C  O  O  H  Pine  needles,  icd  ants,  guano. 

Acetic  "  C  H,  C  O  O  H  Vinegar  and  many  vegetable  juices. 

Propionic       "  C2  Hs  COOH  Yarrow-flowers. 

Butyric  "  C3  H7  C  O  O  H  Butter,limburgercheese,parsnip seeds. 

Valeric  "  C4  H9  C  O  O  H  Valerian  root,  old  cheese. 

Caproic          "  C5  Hn  COOH  Butter,  cocoanut  oil. 

Oenanthylic  "  C0  H13  C  O  O  H  (Artificial.)  [fusel  oil. 

Caprylic         "  C7  H1B  COOH  Butter,  cocoanut  oil,  limburger  cheese, 

Pelargonic     "  C8  HI7  COOH  Rose-geranium. 

Capric  "  C9 II,,,  COOH  Butter,  cocoanut  oil. 

Umbellic        "  Cj0  H21  C  O  O  H  Seeds  of  California  laurel. 

Laurie  "  Cu  Hjg  COOH  Laurel  oil,  butter,  bayberry  tallow. 

Iridecylic     M  CuHjsCOOH  (Artificial.) 


76 


HOW  CHOPS  GROW. 


Myristlc     ac 
Isocetic 
Palmitic 
Margaric 
Stearic 
Nondecylie 
Arachic 
Medullic 
Belienic 

ld,C1lt  H27  C  O  O  H 
CH  H.J9  C  O  O  H 
Gu  H31  C  0  0  H 
C16  Hga  C  O  O  H 
CI7  Hag  C  O  O  H 
C18  H37  C  0  0  H 
C19  H39  C  O  O  H 
C20  H41  C  O  O  H 
C21  H43  C  0  0  H 
CM  H45  C  0  0  H 
C^  H47  C  O  0  H 
C24  H49  C  0  0  H 
CK  H51  C  0  0  H 

Lignoceric 
Hyenic 

Orotio            « 

Nutmeg'oil. 

Seeds  of  Jatropha. 

Butter,  tallow,  lard,  palm  oft. 

(Artificial.) 

Tallow,  lard. 

(Unknown.) 

Butter,  peanut  oil. 

Marrow  of  ox. 

Oil  of  Moringa  oleifera. 

(Unknown.) 

Beech-wood  tar. 

Hyena-fat. 

(Unknown.) 

Beeswax,  carnauba  wax,  wool-fat. 

It  is  to  be  observed  that  these  fatty  acids  make  a  nearly 
complete  series,  the  first  of  which  contains  one  carbon 
and  two  hydrogen  atoms,  and  the  last  27  carbon  and  54 
hydrogen  atoms,  and  that  each  of  the  intermediate  acids 
differs  from  its  neighbors  by  CH2.  The  first  two  acids 
in  this  series  are  thin,  intensely  sour,  odorous  liquids 
that  mix  with  water  in  all  proportions  ;  the  third  to  the 
ninth  inclusive  are  oily  liquids  whose  consistency  in- 
creases and  whose  sourness  and  solubility  in  water  dimin- 
ish with  their  greater  carbon  content.  The  tenth  and 
other  acids  are  at  common  temperatures  nearly  tasteless, 
odorless,  and  fatty  solids,  which  easily  melt  to  oily  liquids 
whose  acid  properties  are  but  feebly  manifest.  Of  these 
acids  a  few  only  require  further  notice. 

Acetic  Acid,  02H402,  or  CH8COOH,  formed  in  the 
"acetic  fermentation"  from  cider,  malt,  wine  and  whis- 
ky, alcohol  being  in  each  case  its  immediate  source, 
exists  free  in  vinegar  to  the  extent  of  about  5  per  cent. 
When  pure,  it  is  a  strongly  acid  liquid,  blistering  the 
tongue,  boiling  at  246°,  and  solidifying  at  about  60°  to  a 
white  crystalline  mass.  In  plants,  acetic  acid  is  said  to 
exist  in  small  proportion,  mostly  as  acetate  of  potassium. 

Butyric  Acid,  C4H802,  or  CH3CH2CH2COOH,  in  the 
free  state,  occurs  in  rancid  butter,  whose  disagreeable 
odor  is  largely  due  to  its  presence.  In  sweet  butter  it 
exists  only  as  a  glyceride  or  fat  of  agreeable  qualities. 


THE  VOLATILE  PAET  OF  PLANTS.  77 

The  other  acids  of  this  series  are  mostly  found  in  veg- 
etable and  animal  fats  or  fatty  oils.  (See  p.  85.) 

OXYFATTY  ACIDS. — The  acids  of  this  class  differ  from 
the  corresponding  fatty  acids  by  having  an  additional 
atom  of  oxygen,  or  by  the  substitution  of  OH  for  H  in 
the  latter.  There  are  two  acids  of  this  class  that  may  be 
briefly  noticed,  viz. :  oxyacetic,  or  glycollic  acid,  and  oxy> 
propionic  or  lactic  acid. 

Glycollic  Acid,  C2H403  or  HOCH2COOH,  exists  in 
the  juices  of  plants  (grape-vine),  and  like  acetic  acid  may 
be  formed  by  oxidizing  alcohol. 

Lactic,  C3H603,  or  CH3CH  (OH)  COOH,  is  the  acid 
that  is  formed  in  the  souring  of  milk,  where  it  is  produced 
from  the  milk-sugar  by  a  special  organized  ferment.  It 
is  also  formed  in  the  "lactic  fermentation"  of  cane- 
sugar,  starch  and  gum,  and  exists  accordingly  in  sour- 
kraut  and  ensilage. 

The  fatty  and  oxyfatty  acids  are  monobasic,  i.e.,  they 
contain  one  carboxyl,  COOH,  and  each  acid  forms  one 
salt  only,  with  potassium,  for  instance,  in  which  the  hy- 
drogen of  the  carboxyl  is  replaced  by  the  metal.  Thus, 
potassium  acetate  is  CH3COOK. 

The  oxyfatty  acids  are  especially  prone  to  form  anhy- 
drides by  loss  of  the  elements  of  water.  Lactic  acid 
cannot  be  obtained  free  from  admixed  water  when  its 
aqueous  solutions  are  evaporated,  without  being  partially 
converted  into  an  anhydride.  Gentle  heat  up  to  270° 
changes  it,  with  loss  of  water,  into  so-called  lactolactic 
acid*  C6H1005,  a  solid,  scarcely  soluble  in  water,  but  that 
slowly  reproduces  lactic  acid  by  contact  with  water,  and 
dissolves  in  alkalies  to  form  ordinary  lactates.  Lacto- 
lactic acid,  heated  to  290°,  loses  water  with  formation 
of  lactide,\  C6H804,  a  solid  nearly  insoluble  in  water,  but 
also  convertible  into  lactic  acid  by  water,  and  into  lactates 
by  alkalies. 

~~*~2  (C.H.OS)  =  C6H1005  +  H,0  t  C6H1006  =  CSH,O4  +  H,O 


78  HOW  CROPS  GROW. 

Dibasic  Acids>  "^The  acids  of  this  class  requiring  notice 

are 

COOH 

OOH 

Malonic  acid,  CSH4O<,  or  CH2 


Oxalic  add,  C.H,O4,  or 

C 


Succinic  acid,  CJ^O^,  or 

C 


CHj—  COOH 


H.—  COOH 
CH2—  COOH 


Malic  acid  (Oxysuccinic  acid),    C4H6O5,  or 

CH(OH)-COOH 
CH(OH)    COOH 

Tartaric  acid    (Dioxysuccinic  CiHgOg,  or 

acid),  CH(OH)    COOH 

The  salts  formed  by  union  of  these  acids  with  metallic 
bases  are  either  primary  or  secondary,  according  as  the 
metal  enters  into  one  or  two  of  the  carboxyls. 

Oxalic  acid,  C2H204,  exists  largely  in  the  common 
sorrel,   and  is  found  in  greater  or  less 
quantity  in  nearly  all  plants.     The  pure 
acid  presents  itself  in  the  form  of  color- 
less, brilliant,    transparent   crystals,   not 
unlike  Epsom  salts  in  appearance   (Fig.          Fig.  15. 
15),  but  having  an  intensely  sour  taste. 

Primary  potassium  oxalate  (formerly  termed  acid  ox- 
alate  of  potash),  HOOC  —  COOK,  occasions  the  sour  taste 
of  the  juice  of  sorrel,  from  which  it  may  be  obtained 
in  crystals  by  evaporating  off  the  water.  It  may  also  be 
prepared  by  dissolving  oxalic  acid  in  water,  dividing  the 
solution  into  two  equal  parts,  neutralizing  *  one  of  these 
by  adding  solution  of  potash  and  then  mixing  the  two 
solutions  and  evaporating  until  crystals  form. 

Secondary  potassium  oxalate  (neutral  oxalate  of  potash), 
KOOC  —  COOK,  is  the  result  of  fully  neutralizing  oxalic 
acid  with  potash  solution.  It  has  no  sour  taste. 

Primary  calcium  oxalate  exists  dissolved  in  the  cells 
of  plants  so  long  as  they  are  in  active  growth.  Second- 
ary calcium  oxalate  is  extremely  insoluble  in  water,  and 

*  As  described  in  Exp.  38. 


THE  VOLATILE  PAET  OF  PLANTS.  79 

Yery  frequently  occurs  within  the  plant  as  microscopic 
crystals.  These  are  found  in  large  quantity  in  the  ma- 
ture leaves  and  roots  of  the  beet,  in  the  root  of  garden 
rhubarb,  and  especially  in  many  lichens. 

Secondary  ammonium  oxalate  is  employed  as  a  test  for 
calcium. 

EXP.  36.— Dissolve  5  grams  of  oxalic  acid  in  50  c.  c.  of  hot  water,  add. 
solution  of  ammonia  or  solid  carbonate  of  ammonium  until  the  odor  of 
the  latter  slightly  prevails,  and  allow  the  liquid  to  cool  slowly.  Long, 
needle-like  crystals  of  ammonium  oxalate  separate  on  cooling,  the 
compound  being  sparingly  soluble  in  cold  water.  Preserve  for  future 

use. 

EXP.  37.— Add  to  any  solution  of  lime,  as  lime-water  (see  note,  p.  20), 
or  hard  well-water,  a  few  drops  of  solution  of  ammonium  oxalate. 
Secondary  Calcium  oxalate  immediately  appears  as  a  white,  powdery 
precipitate,  which,  from  its  extreme  insolubility,  serves  to  indicate  the 
presence  of  the  minutest  quantities  of  lime.  Add  a  few  drops  of  hydro- 
chloric or  nitric  acid  to  the  calcium  oxalate;  it  disappears.  Hence 
ammonium  oxalate  is  a  test  for  lime  only  in  solutions  containing  no  free 
mineral  acid.  (Acetic  and  oxalic  acids,  however,  have  little  effect  upon 
the  test.) 

Malonic  acid  and  Succinic  acid  occur  in  plants  in 
but  small  quantities.  The  former  has  been  found  in 
sugar-beets,  the  latter  in  lettuce  and  unripe  grapes. 

Malic  acid,  C4H605,  is  the  chief  sour  principle  of  ap- 
ples, currants,  gooseberries,  plums,  cherries,  strawberries, 
and  most  common  fruits.  It  exists  in  small  quantity  in  a 
multitude  of  plants.  It  is  found  abundantly  in  the  gar- 
den rhubarb,  and  primary  potassium  malate  may  be  ob- 
tained in  crystals  by  simply  evaporating  the  juice  of  the 
leaf-stalks  of  this  plant.  It  is  likewise  abundant  as  cal- 
cium salt  in  the  nearly  ripe  berries  of  the  mountain  ash, 
and  in  barberries.  Calcium  malate  also  occurs  in  con- 
siderable quantity  in  the  leaves  of  tobacco,  and  is  often 
encountered  in  the  manufacture  of  maple  sugar,  separat- 
ing as  a  white  or  gray  sandy  powder  during  the  evapora- 
tion of  the  sap. 

Pure  malic  acid  is  only  seen  in  the  chemical  laboratory, 
and  presents  white,  crystalline  masses  of  an  intensely 
sour  taste.  It  is  extremely  soluble  in  water. 


80  HOW  CHOPS  GROW. 

Tartaric  acid,  C4H606,  is  abundant  in  the  grape, 
from  the  juice  of  which,  during  fermentation,  it  is  de- 
posited as  argol.  This,  on  purification, 
yields  the  cream  of  tartar  (bitartrate  of 
potash)  of  commerce.  Tartrates  of  po- 
tassium and  calcium  exist  in  small  quan- 
tities in  tamarinds,  in  the  unripe  berries 
of  the  mountain  ash,  in  the  berries  of  the  sumach,  in  cu- 
cumbers, potatoes,  pineapples,  and  many  other  fruits. 
The  acid  itself  may  be  obtained  in  large  glassy  crystals 
(see  Fig.  16),  which  are  very  sour  to  the  taste. 

Of  the  Tribasic  Acids  known  to  occur  in  plants,  but 
one  need  be  noticed  here,  viz.,  citric  acid. 

C  H2  C  O  O  H 

C6H80T,or  C(OH)COOH 
C  Ha  C  0  O  H 

Citric  acid  exists  in  the  free  state  in  the  juice  of  the 
lemon,  and  in  unripe  tomatoes.  It  accompanies  malic 
acid  in  the  currant,  gooseberry,  cherry,  strawberry,  and 
raspberry.  It  is  found  in  small  quantity  in  tobacco 
leaves,  in  the  tubers  of  the  artichoke  (Helianthus),  in  the 
bulbs  of  onions,  in  beet-roots,  in  coffee-berries,  in  seeds  of 
lupin,  vetch,  the  pea  and  bean,  and  in  the  needles  of  the 
fir  tree,  mostly  as  potassium  or  calcium  salt.  It  also 
exists  in  cows'  milk. 

In  the  pure  state,  citric  acid  forms  large  transparent  or 
white  crystals,  very  sour  to  the  taste. 

Relations  of  the  Vegetable  Acids  to  each  other,  and  to  the  Amyloses.-* 
Oxalic,  malic,  tartaric  and  citric  acids  usually  occur  together  in  our 
ordinary  fruits,  and  some  of  them  undergo  mutual  conversion  in  the 
living  plant. 

According  to  Liebig,  the  unripe  berries  of  the  mountain  ash  contain 
much  tartaric  acid,  which,  as  the  fruit  ripens,  is  converted  into  malic 
acid.  Tartaric  acid  can  be  artificially  transformed  into  malic  acid,  and 
this  into  succinic  acid. 

When  citric,  malic  and  tartaric  acids  are  boiled  with  nitric  acid,  or 
heated  with  caustic  potash,  they  all  yield  oxalic  acid. 

Cellulose,  starch,  dextrin,  the  sugars,  yield  oxalic  acid  when  heated 


THE  VOLATILE  PART  02  PLANTS.  81 

with  potash  or  nitric  acid.    Commercial  oxalic  acid  is  thus  made  from 
sawdust. 

Gum  (Arabic),  sugar  and  starch  yield  tartaric  acid  by  the  action  of 
nitric  acid. 

Definition  of  Adds ,  Bases,  and  Salts. — In  the  popular 
sense,  an  acid  is  any  body  having  a  sour  taste.  It  is,  in 
fact,  true  that  all  sour  substances  are  acids,  but  all  acids 
are  not  sour,  some  being  tasteless,  others  bitter,  and  some 
sweet.  A  better  characteristic  of  an  acid  is  its  capability 
of  forming  salts  by  its  interaction  with  bases.  The  strong- 
est acids,  i.  e.,  those  bodies  whose  acid  characters  are  most 
highly  developed,  if  soluble,  so  as  to  have  any  effect  on 
the  nerves  of  taste,  are  sour,  viz.,  sulphuric  acid,  phos- 
phoric acid,  nitric  acid,  etc. 

Bases  are  the  opposite  of  acids.  The  strongest  bases, 
when  soluble,  are  bitter  and  biting  to  the  taste,  and  cor- 
rode the  skin.  Potash,  soda,  lime,  and  ammonia  are  ex- 
amples. Magnesia,  oxide  of  iron,  and  many  other  com- 
pounds of  metals  with  oxygen,  are  insoluble  bases,  and 
hence  destitute  of  taste.  Potash,  soda,  and  ammonia 
are  termed  alkalies  ;  lime  and  magnesia,  alkali-earths. 

Salts  are  compounds  that  result  from  the  mutual  ac- 
tion of  acids  and  bases.  Thus,  in  Exp.  20,  the  salt,  cal- 
cium phosphate,  was  produced  by  bringing  together 
phosphoric  acid,  and  the  base,  lime.  In  Exp.  37,  cal- 
cium oxalate  was  made  in  a  similar  manner.  Common 
salt — in  chemical  language,  sodium  chloride — is  formed 
when  caustic  soda  is  mixed  with  hydrochloric  acid,  water 
being,  in  this  case,  produced  at  the  same  time. 

NaOH  +  HCl  NaCl         +  H,O 

Sodium  hydroxide.    Hydrochloric  acid.    Sodium  chloride.         Water. 

In  general,  salts  having  a  metallic  base  are  formed  by 
substituting  the  metal  for  the  hydrogen  of  the  acid  ;  or  if 
an  organic  acid,  for  the  hydrogen  that  is  united  to  oxy- 
gen, i.e.,  of  carboxyl,  COOH. 

Ammonia,  NH8,  and  many  organic  bases  unite  directly 
to  acids  in  forming  salts. 
6 


82  HOW  CHOPS  GROW. 

NH3  +  HC1  NH4C1 

Ammonia.  Hydrochloric  acid.  Ammonium  chloride.* 

NH3  +  CH3COOH  CH3COONH4 

Ammonia.  Acetic  acid.  Ammonium  Acetate. 

Test  for  acids  and  alkalies. — Many  vegetable  colors  are  altered  by  sol- 
uble acids  or  soluble  bases  (alkalies),  in  such  a  manner  as  to  answer  the 
purpose  of  distinguishing  these  two  classes  of  bodies.  A  solution  of 
cochineal  may  be  employed.  It  has  a  ruby-red  color  when  coiicen-. 
trated,  but,  on  mixing  with  much  pure  water,  becomes  orange  or  yel- 
lowish-orange. Acids  do  not  affect  this  color,  while  alkalies  turn  it  to 
an  intense  carmine  or  violet-carmine,  which  is  restored  to  orange  by 
acids. 

EXP.  38. — Prepare  tincture  t  of  cochineal  by  pulverizing  3  grams  of 
cochineal,  and  shaking  frequently  with  a  mixture  of  50  c.  c.  of  strong 
alcohol  and  200  c.  c.  of  water.  After  a  day  or  two,  pour  off  the  clear 
liquid  for  use. 

To  a  cup  of  water  add  a  few  drops  of  strong  sulphuric  acid,  and  to  an- 
other similar  quantity  add  as  many  drops  of  ammonia.  To  these  liquids 
add  separately  5  drops  of  cochineal  tincture,  observing  the  coloration 
in  each  case.  Divide  the  dilute  ammonia  into  two  portions,  and  pour 
into  one  of  them  the  dilute  acid,  until  the  carmine  color  just  passes  into 
orange.  Should  excess  of  acid  have  been  incautiously  used,  add  am- 
monia, until  the  carmine  reappears,  and  destroy  it  again  by  new  por- 
tions of  acid,  added  dropwise.  The  acid  and  base  thus  neutralize  each 
other,  and  the  solution  contains  sulphate  of  ammonia,  but  no  free  acid 
or  base.  It  will  be  found  that  the  orange-cochineal  indicates  very  mi- 
nute quantities  of  ammonia,  and  the  carmine-cochineal  correspond- 
ingly small  quantities  of  acid. 

In  the  formation  of  salts,  the  acids  and  bases  more  or 
less  neutralize  each  other's  properties,  and  their  com- 
pounds, when  soluble,  have  a  less  sour  or  less  acrid  taste, 
and  act  less  vigorously  on  vegetable  colors  than  the  acids 
or  bases  themselves.  Some  soluble  salts  have  no  taste 
at  all  resembling  either  their  base  or  acid,  and  have 
no  effect  on  vegetable  colors.  This  is  true  of  common 
salt,  glauber  salts  or  sulphate  of  sodium,  and  saltpeter  or 
nitrate  of  potassium.  Others  exhibit  the  properties  of  their 
base,  though  in  a  reduced  degree.  Carbonate  of  am- 
monium, for  example,  has  much  of  the  odor,  taste,  and 


*  Also  termed  ammonic  chloride,  ammonia  hydrochlorate,  ammonia 
hydrochloride,  and  formerly  muriate  of  ammonia. 

t  Tinctures,  in  the  language  of  the  apothecary,  are  alcoholic  solutions. 
Tincture  of  litmus  (procurable  of  the  apothecary),  or  of  dried  red  cab- 
bage, may  also  be  employed.  Litmus  is  made  red  by  soluble  acids,  and 
blue  by  soluble  bases.  With  red  cabbage,  acids  develop  a  purple,  and 
the  bases  a  green  color. 


THE  VOLATILE  PART  Of  PLANTS. 


effect  on  vegetable  colors  that  belong  to  ammonia.  Car- 
bonate of  sodium  has  the  taste  and  other  properties  of  caus- 
tic soda  in  a  greatly  mitigated  form.  On  the  other  hand, 
sulphates  of  aluminum,  iron,  and  copper,  have  slightly 
acid  characters. 

5.  FATS  AND  OILS  (WAX). — We  have  only  space  here 
to  notice  this  important  class  of  bodies  in  a  very  general 
manner.  In  all  plants  and  nearly  all  parts  of  plants  we 
find  some  representatives  of  this  group  ;  but  it  is  chiefly 
in  certain  seeds  that  they  occur  most  abundantly.  Thus 
the  seeds  of  hemp,  flax,  colza,  cotton,  bayberry,  peanut, 
butternut,  beech,  hickory,  almond,  sunflower,  etc.,  con- 
tain 10  to  70  per  -cent  of  oil,  which  may  be  in  great  part 
removed  by  pressure.  In  some  plants,  as  the  common 
bayberry  and  the  tallow-tree  of  Nicaragua,  the  fat  is 
solid  at  ordinary  temperatures,  and  must  be  extracted  by 
aid  of  heat ;  while,  in  most  cases,  the  fatty  matter  is 
liquid.  The  cereal  grains,  especially  oats  and  maize,  con- 
tain oil  in  appreciable  quantity.  The  mode  of  occur- 
rence of  oil  in  plants  is  shown  in  Fig.  17,  which  repre- 
sents a  highly  magnified  section  of  the  flax-seed.  The 
oil  exists  as  minute,  transparent  globules  in  the  cells,/. 
From  these  seeds  the  oil  may  be  completely  extracted  by 
ether,  benzine,  or  sulphide  of  car- 
bon, which  dissolve  all  fats  with 
readiness,  but  scarcely  affect  the 
other  vegetable  principles. 

Many  plants  yield  small  quanti- 
ties of  wax,  which  often  gives  a 
glossy  coat  to  their  leaves,  or 
forms  a  bloom  upon  their  fruit. 
The  lower  leaves  of  the  oat-plant 
at  the  time  of  blossom  contain,  in 
the  dry  state,  10  per  cent  of  fat 
and  wax  (Arendt).  Scarcely  two 


Fig.  17. 


of  these  oils,  fats,  or  kinds  of  wax,  are  exactly  alike  in 


84  HOW  CEOPS  GROW. 

their  properties.  They  differ  more  or  less  in  taste,  odor, 
and  consistency,  as  well  as  in  their  chemical  composition. 
The  "oils"  are  the  simplest  in  chemical  composition, 
and  have  the  lowest  melting  points.  The  "fats"  have 
larger  content  of  carbon,  and  higher  points  of  fusion. 
The  varieties  of  wax  are  most  complex  in  composition, 
and  have  the  highest  melting  points  and  greatest  content 
of  carbon.  These  differences  are  mostly  gradational.  In 
chemical  constitution  these  bodies  are  alike. 

EXP.  39. — Place  a  handful  of  fine  and  fresh  corn  or  oatmeal,  which  has 
been  dried  for  an  hour  or  so  at  a  heat  not  exceeding  212°,  in  a  bottle. 
Pour  on  twice  its  bulk  of  ether,  cork  tightly,  and  agitate  frequently  for 
half  an  hour.  Drain  off  the  liquid  (filter,  if  need  be)  into  a  clean  porce- 
lain dish,  and  allow  the  ether  to  evaporate.  A  yellowish  oil  remains, 
which,  by  gently  warming  for  some  time,  loses  the  smell  of  ether  and 
becomes  quite  pure. 

The  fatty  oils  must  not  be  confounded  with  the  ethe- 
real, essential,  or  volatile  oils,  which,  however,  do  not  occur 
to  much  extent  in  agricultural  plants.  The  former  can 
not  evaporate  except  at  a  high  temperature,  and  when 
brought  upon  paper  leave  a  permanent  "grease  spot." 
The  latter  readily  volatilize,  leaving  no  trace  of  their 
presence.  The  former,  when  pure,  are  without  smell  or 
taste.  The  latter  usually  possess  marked  odors,  which 
adapt  many  of  them  to  use  as  perfumes. 

In  the  animal  body,  fat  (in  some  insects,  wax)  is  formed 
or  appropriated  from  the  food,  and  accumulates  in  con- 
siderable quantities.  How  to  feed  an  animal  so  as  to 
cause  the  most  rapid  and  economical  fattening  is  one  of 
the  most  important  questions  of  agricultural  chemistry. 

However  greatly  the  various  fats  may  differ  in  external 
characters,  they  are  all  mixtures  of  a  few  elementary  fats. 
The  most  abundant  and  commonly-occurring  fats,  espe- 
cially those  which  are  ingredients  of  the  food  of  man  and 
domestic  animals — e.g.,  tallow,  olive  oil,  and  butter — con- 
sist mainly  of  three  substances,  which  we  may  briefly 
notice.  These  elementary  fats  are  Stearin,  Palmitin, 


THE  VOLATILE  PART  OF  PLANTS.  85 

and  Olein,*  and  they  consist  of  carbon,  oxygen,  and  hy- 
drogen, the  first-named  element  being  greatly  prepon- 
derant. 

Stearin  is  represented  by  the  formula  C57H11006.  It 
is  the  most  abundant  ingredient  of  the  common  fats,  and 
exists  in  largest  proportion  in  the  harder  kinds  of  tallow. 

EXP.  40.— Heat  mutton  or  beef  tallow  in  a  bottle  that  may  be  tightly 
corked,  with  ten  times  its  bulk  of  concentrated  ether,  until  a  clear 
solution  is  obtained.  Let  cool  slowly,  when  stearin  will  crystallize  out 
in  pearly  scales. 

Palmitin,  C51H9806,  receives  its  name  from  the  palm 
oil,  of  Africa,  in  which  it  is  a  large  ingredient.  It  forms 
a  good  part  of  butter,  and  is  one  of  the  chief  constituents 
of  beeswax,  and  of  bayberry  tallow. 

Olein,  C67H1(H06,  is  the  liquid  ingredient  of  fats, 
and  occurs  most  abundantly  in  the  oils.  It  is  prepared 
from  olive  oil  by  cooling  down  to  the  freezing  point, 
when  the  stearin  and  the  palmitin  solidify,  leaving  the 
olein  still  in  the  liquid  state. 

Other  elementary  fats,  viz.,  butyrin,  laurin,  myristin,  etc.,  occur  in 
small  quantity  in  butter,  and  in  various  vegetable  oils.  Flaxseed  oil 
contains  linolein ;  castor  oil,  ricinolein,  etc. 

We  have  already  given  the  formulae  of  the  principal 
fats,  but  for  our  purposes,  a  better  idea  of  their  composi- 
tion may  be  gathered  from  a  centesimal  statement,  viz. : 

CENTESIMAL  COMPOSITION  OF  THE  ELEMENTARY  FATS. 

Stearin.  Palmitin.  Olein. 

Carbon 76.6              75.9  77.4 

Hydrogen 12.4              12.2  11.8 

Oxygen 10.0             11.9  10.8 

100.0  100.0  100.0 

Saponification. — The  fats  are  characterized  by  forming 
soaps  when  heated  with  strong  potash  or  soda-lye.  They 
are  by  this  means  decomposed,  and  give  rise  to  fatty 

*  Marffarin,  formerly  thought  to  be  a  chemically-distinct  fat,  is  a  mix- 
ture of  stearin  and  palmitin.  Oleomargarine  is  the  commercial  designa- 
tion of  an  artificially-obtained  mixture  of  fats,  animal  or  vegetable, 
that  has  nearly  the  consistence  of  dairy  buttei. 


86  HOW  CEOPS  GROW. 

acidt,  which  remain  combined  with  the  alkali-metal, 
and  to  glycerin,  a  substance  which  acts  as  a  base.  The 
fats  are  therefore  termed  glycerides. 

EXP.  41. — Heat  a  bit  of  tallow  with  strong  solution  of  caustic  potash 
until  it  completely  disappears,  and  a  soap,  soluble  in  water,  is  obtained. 
To  one-half  the  hot  solution  of  soap,  add  hydrochloric  acid  until  the  lat- 
ter predominates.  An  oil  will  separate  which  gathers  at  the  top  of  the 
liquid,  and,  on  cooling,  solidifies  to  a  cake.  This  is  not,  however,  the 
original  fat.  It  has  a  different  melting  point,  and  a  different  chem- 
ical composition.  It  is  composed  of  the  three  fatty  acids,  corres- 
ponding to  the  elementary  fats  from  which  it  was  produced. 

When  saponified  by  the  action  of  potash,  stearin  yields 
stearic  acid,  Ci8H8602 ;  palmitin  yields  palmitic  acid, 
C16H8202 ;  and  olein  gives  oleic  acid,  C18H3402.*  The 
so-called  stearin  candles  are  a  mixture  of  stearic  and 
palmitic  acids.  The  glycerin,  C8H808,  that  is  simul- 
taneously produced,  remains  dissolved  in  the  liquid. 
Glycerin  is  found  in  commerce  in  a  nearly  pure  state,  as 
a  colorless,  syrupy  liquid,  having  a  pleasant,  sweet  taste. 

The  chemical  act  of  saponiflcation  consists  in  the  re-arrangement  of 
the  elements  of  one  molecule  of  fat  and  three  molecules  of  water  into 
three  molecules  of  fatty  acid,  and  one  molecule  of  glycerin. 

Palmitin.  Water.  Palmitic  acid.  Glycerin. 

CsiH^Oe        +      3(H20)        =       3  (C16H32O2)         +         C3H8OS 

Saponification  is  likewise  effected  by  the  influence  of  strong  acids 
and  by  heating  with  water  alone  to  a  temperature  of  near  400°  F. 

Ordinary  soap  is  nothing  more  than  a  mixture  of  stearate,  palmitate, 
and  oleate  of  potasssium  or  of  sodium,  with  or  without  glycerin.  Com- 
mon soft  soap  consists  of  the  potassium  compounds  of  the  above- 
named  acids,  mixed  with  glycerin  and  water.  Hard  soap  is  usually  the 
corresponding  sodium-compound,  free  from  glycerin.  When  soft  soap 
is  boiled  with  common  salt  (chloride  of  sodium),  hard  soap  and  chlo- 
ride of  potassium  are  formed  by  transposition  of  the  ingredients.  On 
cooling,  hard-soap  forms  a  solid  cake  upon  the  liquid,  and  the  glycerin 
remains  dissolved  in  the  latter. 

Relations  of  Fats  to  Carbhydrates. — The  oil  or  fat  of 
plants  is  in  many  cases  a  product  of  the  transformation 
of  starch  or  other  member  of  the  cellulose  group,  for  the 
oily  seeds,  when  immature,  contain  starch,  which  van- 

*  Oleic  acid  differs  from  stearic  acid  in  containing  two  atoms  less  ol 
hydrogen,  and  is  one  of  a  series  that  bear  this  relation  to  the  fatty  acids 
of  corresponding  content  of  carbon. 


THE  VOLATILE  PAST  OF  PLANTS.        87 

ishes  as  they  ripen,  and  in  the  sugar-cane  the  quantity 
of  wax  is  said  to  be  largest  when  the  sugar  is  least  abund- 
ant, and  vice  versa.  In  germination  the  oil  of  the  seed 
is  converted  back  again  into  starch,  sugar,  etc. 

The  Estimation  of  Fat  (including  wax)  is  made  by  warming  the  pul- 
verized and  dry  substance  repeatedly  with  renewed  quantities  of  ethef , 
or  sulphide  of  carbon,  as  long  as  the  solvent  takes  up  anything.  On 
evaporating  the  solutions,  the  fat  remains,  and  after  drying  thorough- 
ly, may  be  weighed.  The  ether  extract  thus  obtained  is  usually  accom- 
panied by  a  small  amount  of  other  substances,  especially  chlorophyll 
and  lecithin,  and  is  hence  properly  termed  crude  fat. 

PROPORTIONS  OF  CRUDE  FAT  EN  VARIOUS  VEGETABLE  PRODUCTS. 

Per  cent.  Per  cent. 

Meadow  grass 0.8       Turnip 0.1 

Red  clover  (green) 0.7       Wheat  kernel 1.6 


Cabbage 0.4       Oat 

Meadow  hay 3.0       Maize 

Clover  hay 3.2       Pea 


1.6 
7.0 
.3.0 
Wheat  straw 1.5       Cotton  se  d 34.0 


Oat  straw 2.0       Flax 

Wheat  bran 1.5       Colza 

Potato  tuber 0.3 


.34.0 
.45.0 


6.  THE  ALBUMINOIDS  OR  PROTEIDS. — The  bodies  of 
this  class  essentially  differ  from  those  of  the  groups  hith- 
erto noticed,  in  the  fact  of  their  containing,  in  addition 
to  carbon,  oxygen,  and  hydrogen,  15  to  18  per  cent  of 
nitrogen,  with  a  small  quantity  of  sulphur,  and,  in  some 
cases,  perhaps  phosphorus. 

These  bodies,  though  found  in  some  proportion  in  all 
parts  of  plants,  being  everywhere  necessary  to  growth, 
are  chiefly  accumulated  in  the  seeds,  especially  in  those 
of  the  cereal  and  leguminous  grains. 

The  albuminoids  or  proteids*  that  occur  in  plants  are 
so  similar,  in  many  characters,  to  those  which  constitute 
a  large  portion  of  every  animal  organism,  that  we  may 
advantageously  consider  them  in  connection  with  the 
latter. 

*  The  nomenclature  of  these  substances  is  unavoidably  confused. 
They  are  often  termed  nitrogenous  or  nitrogenized  bodies,  also  albu« 
minous  bodies,  and  protein  bodies.  The  term  albuminoids  has  been 
latterly  restricted,  by  some  authors,  to  the  substances  of  which  gel» 
tine  is  a  type.  The  word  albuminates  is  applied  to  syiitouin  an<J 
casein. 


88  HOW  CBOPS  GBOW. 

Three  familiar  representatives  of  this  class  of  bodies 
are,  albumin,  or  the  white  of  egg  ;  fibrin,  or  the  clot  of 
blood,  and  casein,  which  yields  the  curd  of  milk. 

General  Characters. — Many  of  these  substances  occur 
in  two  very  distinct  modifications,  one  form  being  soluble 
in  water,  or  in  highly-diluted  acids  or  alkalies,  or  in  salt- 
solutions,  the  other  insoluble  in  these  liquids. 

Some  of  the  soluble  proteids  we  find  naturally  dissolved 
in  the  juices  of  living  plants  and  animals.  Some  may  be 
obtained  in  the  solid  form  by  evaporating  off  at  a  very 
gentle  heat  the  water  which  is  naturally  associated  with 
them.  They  then  appear  as  nearly  colorless  or  yellow- 
ish, amorphous  solids,  destitute  of  odor  or  taste,  which 
dissolve  again  in  water,  but  are  insoluble  in  alcohol. 

Soluble  compounds  of  proteids  with  magnesium  or 
iron  occur  in  plants,  or  may  be  obtained  from  the  blood 
of  animals,  in  the  form  of  white  or  red  crystals. 

Solutions  of  most  of  the  albuminoids  are  readily  coagu- 
lated by  heat  and  by  concentrated  mineral  acids,  the 
albuminoids  being  thereby  themselves  chemically  changed 
and  made  insoluble.  Some  coagulate  spontaneously. 

The  insoluble  albuminoids,  some  of  which  also  occur 
naturally  in  plants  and  animals,  are,  when  purified  as 
much  as  possible,  white,  flocky,  lumpy  or  fibrous  bodies, 
quite  odorless  and  tasteless. 

The  albuminoids,  when  subjected  to  heat,  melt  and 
burn  with  a  smoky  flame  and  a  peculiar  odor — that  of 
burnt  hair  or  horn — while  a  shining  charcoal  remains 
which  is  difficult  to  consume. 

Tests  for  the  Albuminoids.— The  chemist  employs  the  behavior  of 
the  albuminoids  towards  a  number  of  reagents*  as  tests  for  their  pres- 
ence. Some  of  these  are  so  delicate  and  characteristic  as  to  allow  the 


*  Reagents  are  substances  commonly  employed  for  the  recognition 
of  bodies,  or,  generally,  to  produce  chemical  changes.  All  chemical 
phenomena  result  from  the  mutual  action  of  at  least  two  elements, 
which  thus  act  and  react  on  each  other.  Hence  the  substance  that 
excites  chemical  changes  is  termed  a  reagent,  and  the  phenomena  or 
results  of  its  application,  are  called  reactions, 


THE  VOLATILE  PABT  OF  PLANTS.         89 

distinction  of  this  class  of  substances  from  all  others,  even  in  micro- 
scopic observations. 

1.  Solution  of  iodine  colors  them  intensely  yellow  or  bronze. 

2.  "Warm    and   strong  hydrochloric  acid  colors   these   bodies   blue, 
violet,  or  brown,  or,  if  applied  in  large  excess,  dissolves  them  to  a 
liquid  of  these  colors. 

3.  In  contact  with  nitric  acid,  especially  when  hot,  they  are  stained  a 
deep  [and  vivid  yellow.    Silk  and  wool,  which  consist  largely  of  pro- 
teids,  are  commonly  dyed  or  printed  yellow  by  means  of  nitric  acid. 

4.  A  solution  of  mercuric  nitrate  in  excess  of  nitric  acid,*  tinges  them 
of  a  deep  red  color.    This  test  enables  us  to  detect  albumin,  for  exam- 
ple, eveu  where  it  is  dissolved  in  20,000  parts  of  water. 

5.  With   caustic  soda  and  very  dilute  solution  of  copper  sulphate, 
successively  applied,  the  proteids  give  a  violet  color  which  is  intensi- 
fied by  warming.    (Biuret  test.) 

The  Albumins  are  soluble  in  water;  the  solutions  as 
naturally  occurring,  unless  very  dilute,  are  coagulated  by 
heat. 

Egg  Albumin. — The  white  of  a  hen's  egg  on  drying 
yields  ^bout  12  per  cent  of  albumin  in  a  state  of  tol- 
erable purity.  The  fresh  white  of  eggs  serves  to  illus- 
trate the  peculiarities  of  this  substance,  and  to  exhibit 
the  deportment  of  the  albuminoids  generally  toward  the 
above-named  reagents. 

EXP.  42.— Beat  or  whip  the  white  of  an  egg  so  as  to  destroy  the  deli- 
cate transparent  membrane  in  the  cells  of  which  the  albumin  is  held, 
and  agitate  a  portion  of  it  with  water  ;  observe  that  it  mostly  dissolves 
in  the  latter.  The  solution  is  turbid  from  presence  of  globulin. 

EXP.  43. — Heat  a  part  of  the  undiluted  white  of  egg  in  a  tube  or  cup. 
At  165°  F.  it  becomes  opaque,  white,  and  solid  (coagiilates),  and  is  con- 
verted into  the  insoluble  modification.  A  higher  heat  is  needful  to 
coagulate  solutions  of  albumin,  in  proportion  as  they  are  diluted  with 
water. 

EXP.  44. — Add  strong  alcohol  to  a  portion  of  the  solution  of  albumin 
of  Exp.  42.  It  precipitates  the  albumin,  which  for  a  time  remains  solu- 
ble in  water,  but  later  coagulates  and  becomes  insoluble. 

EXP.  45. — Observe  lhat  albumin  is  coagulated  by  strong  acids  applied 
in  small  quantify,  especially  by  nitric  acid. 

EXP.  46.— Put  a  little  albumin,  either  soluble  or  coagulated,  into  each 
of  five  test  tubes.  To  one,  add  solution  of  iodine;  to  a  second,  strong 
hydrochloric  acid;  to  a  third,  nitric  acid;  to  a  fourth,  nitrate  of  mer- 
cury, and  to  the  last  a  few  drops  of  solution  of  copper  sulphate,  and 
then  a  little  caustic  soda  or  potash  solution.  Observe  the  characteristic 
colorations  that  appear  immediately,  or  after  a  time,  as  described 
above.  In  the  last  four  cases  the  reaction  is  hastened  by  a  gentle  heat. 


•Tliis  solution,  known  as  Millon's  reagent,  is  prepared  by  dissolving 
mercury  in  its  own  weight  of  nitric  acid  of  sp.  gr.  1.4,  heating  toward 
the  close  of  the  process,  and  finally  adding  to  the  liquid  twice  its  buUc 
of  water. 


90  HOW  CEOPS  GROW. 

Serum  Albumin  occurs  dissolved  in  the  blood,  in  milkj 
and  in  nearly  all  the  liquids  of  the  healthy  animal  body  ex- 
cept the  urine.  Its  characters  are  slightly  different  from 
those  of  egg-albumin.  The  albumin  of  the  blood  maj 
be  separated  by  heating  blood-serum  (the  clear  yellow 
liquid  that  floats  above  the  clot).  The  albumin  of  milk 
coagulates  when  milk-serum  (whey)  is  heated  to  near 
boiling. 

On  boiling  entire  milk,  albumin  coagulates,  and,  mixed 
with  fat  and  casein,  is  deposited  as  a  tough  coating  on 
the  sides  of  the  vessel. 

Animal  albumin  remains,  when  its  solutions  are  evap- 
orated at  a  temperature  below  140°  F.,  as  a  yellowish  trans- 
lucent and  friable  solid,  which  easily  dissolves  in  water. 

Vegetable  Albumin. — In  the  juices  of  all  plants  is 
found  in  small  quantity  a  substance  which  agrees  in 
many  respects  with  animal  albumin,  and  has  been  termed 
vegetable  albumin.  The  clear  juice  of  the  potato  tuber 
(which  may  be  procured  by  grating  potatoes,  squeezing 
the  pulp  in  a  cloth,  and  letting  the  liquor  thus  obtained 
stand  in  a  cool  place  until  the  starch  has  deposited)  con- 
tains such  a  body  in  solution,  as  may  be  shown  by  heat- 
ing to  near  the  boiling  point,  when  a  coagulum  separates, 
which,  after  boiling  successively  with  alcohol  and  ether 
to  remove  fat  and  coloring  matters,  in  its  chemical  reac- 
tions and  composition  closely  approaches  the  coagulated 
albumin  of  eggs. 

The  juice  of  succulent  vegetables,  as  cabbage,  yields 
a  similar  substance  in  larger  quantity,  though  less  pure, 
by  the  same  treatment. 

Water  which  has  been  agitated  for  some  time  in  con- 
tact with  flour  of  wheat,  rye,  oats,  or  barley,  is  found 
by  the  same  method  to  have  extracted  an  albuminoid  from 
these  grains. 

The  coagulum,  thus  prepared  from  any  of  these  sources,  exhibits  th« 
reactions  characteristic  of  the  albuminoids,  when  put  in  contact  wilfc 
nitrate  of  mercury,  nitric  or  hydrochloric  acid. 


THE  VOLATILE  PART  OE  PLANTS.  91 

EXP.  47.— Prepare  impure  vegetable  albumin  from  potatoes,  cabbage, 
or  flour,  as  above  described,  and  apply  the  nitrate  of  mercury  test. 

As  already  intimated,  albumin  is  chemically  changed 
or  decomposed  in  the  process  of  coagulation.  Coagu- 
lated albumin  is  not  readily  dissolved  by  dilute  acids  or 
by  dilute  aqueous  solutions  of  alkali. 

The  so-called  vegetable  albumin  is  mostly  known  only 
after  coagulation  by  heat,  and  has  been  but  imperfectly 
studied.  According  to  Eitthausen,  the  coagulum  ob- 
tained by  heating  the  juice  of  potato  tubers  or  the  aque- 
ous extracts  of  peas  and  horse-beans  (  Vicia  faba)  is  solu- 
ble in  dilute  potash  and  in  acetic  acid ;  it  is  therefore 
not  albumin.  Sidney  Martin  reports  a  genuine  albumin 
in  the  juice  of  the  papaw,  but  its  composition  has  not 
been  determined. 

Fibrin. — Animal  Fibrin  is  insoluble  in  water,  alco- 
hol and  salt-solutions ;  it  swells  up  in  dilute  acids,  dis- 
solves in  alkalies,  and  is  coagulated  by  heat. 

The  blood  of  the  higher  animals,  when  in  the  body  or 
when  fresh  drawn,  is  perfectly  fluid.  Shortly  after  it  is 
taken  from  the  veins  it  partially  solidifies — it  coagulates 
or  becomes  clotted.  It  hereby  separates  into  two  por- 
tions, a  clear,  pale-yellow  liquid — the  serum — and  the 
clot.  As  already  stated,  the  serum  contains  albumin. 
On  persistently  squeezing  and  washing  the  clot  with 
water,  the  coloring  matter  of  the  blood  is  removed,  and 
a  white  stringy  mass  remains,  which  consists  chiefly  of 
fibrin,  being  a  decomposition-product  of  another  albu- 
minoid, fibrinogen. 

In  very  dilute  hydrochloric  acid,  fibrin  swells  up,  but 
does  not  dissolve.  When  freshly  prepared,  it  absorbs 
oxygen  from  the  air  and  gives  off  carbon  dioxide.  Heat- 
ing to  176°  to  212°  coagulates  and  shrinks  it,  and  ren- 
ders it  less  elastic  and  incapable  of  absorbing  oxygen. 

EXP.  48. — Observe  the  separation  of  blood  into  serum  and  clot ;  coag- 
ulate the  albumin  of  the  former  by  heat,  and  test  it  with  warm  hydro- 
chloric acid.  Tie  up  the  clot  in  a  piece  of  muslin,  and  squeeze  and 


92  HOW  CROPS  GROW. 

wash  In  water  until  coloring  matter  ceases  to  run  off.    Warm  it  with 
nitric  acid  as  a  test. 

Flesh- Fibrin. — If  a  piece  of  lean  beef  or  other  dead 
animal  muscle  be  repeatedly  squeezed  and  washed  in 
water,  the  coloring  matters  are  gradually  removed  and  a 
white  residue  is  obtained  which  resembles  blood-fibrin  ia 
its  external  characters,  and  as  it  represents  the  fibers  of 
the  original  muscle,  and  was  supposed  to  be  a  simple 
albuminoid,  it  was  formerly  designated  flesh-fibrin.  It 
is,  however,  a  mixture  consisting  largely  of  myosin  (see 
p.  97).  It  mostly  dissolves  in  very  dilute  hydrochloric 
acid  to  a  clear  liquid,  from  which  addition  of  much  com- 
mon salt,  or  of  a  little  alkali,  throws  down  syntonin. 
The  term  flesh-fibrin  is  therefore  no  longer  properly  em- 
ployed to  designate  a  distinct  chemical  substance. 

Vegetable  fibrin. — When  wheat-flour  or  rye-flour  is 
mixed  with  a  little  water  to  a  thick  dough,  and  this  is 
washed  and  kneaded  for  some  time  in  water,  the  starch 
and  albumin  are  mostly  removed,  and  a  yellowish  tena- 
cious mass  remains,  which  bears  the  name  gluten.  When 
wheat  is  slowly  chewed,  the  saliva  carries  off  the  starch 
and  other  matters,  and  the  gluten  mixed  with  bran  is 
left  behind — well-known  to  country  lads  as  "  wheat- 
gum." 

EXP.  49. — Wet  a  handful  of  good,  fresh,  wheat-Hour  slowly  with  a  lit- 
tle water  to  a  sticky  dough,  and  squeeze  this  under  a  fine  stream  of 
water  until  the  latter  runs  off  clear.  Heat  a  portion  of  this  gluten  with 
Millon's  reagent. 

Gluten  is  a  mixture  of  several  albuminoids,  and  con- 
tains also  some  starch  and  fat.  When  boiled  with  alco- 
hol it  is  partially  dissolved.*  The  portion  insoluble  in 

*The  dissolved  portion  Ritthausen  found  to  consist  of  two  distinct 
albuminoid  or  rather  f/hitinoi<l  bodies,  viz;. : 

Gliartin,  or  vegetable  glue,  is  very  soluble  in  water  and  alcohol.  It 
strongly  resembles  animal  glue  aiid  chiefly  gives  to  wheat  dough  its 
tenacious  qualities. 

Afiicerfin  resembles  gliadin,  but  is  less  soluble  in  strong  alcohol,  and 
is  insoluble  in  water.  When  moist,  it  is  yellowish-white  in  color,  has 
a  silky  luster,  and  slimy  consistence.  It  exists  also  in  gluten  made 
from  rye  grain.  (Ritthausen,  Jour.  J'ilr  Prukt,  Chem.,  88, 141,  and  99, 463.i 


THE  VOLATILE  PART  OF  PLANTS.  93 

strong  alcohol  Liebig  first  designated  as  vegetable  fibrin. 
Ritthausen  found  this  to  be  a  mixture  of  two  bodies, 
which  he  distinguished  as  gluten-casein  and  gluten-fibrin. 
The  latter  is  extracted  from  gluten  by  hot  weak  alcohol 
and  separates  on  partially  removing  the  alcohol  by  evap- 
oration. 

The  albuminoids  of  crude  gluten  dissolve  in  very  dilute  potash-solu- 
tion (i  to  1  parts  potasli  to  1,000  parts  of  water),  and  the  liquid,  after 
standing  some  days  at  rest,  may  be  poured  off  from  any  residue  of 
starch.  On  adding  acetic  acid  in  slight  excess,  the  purified  albuminoids 
are  separated  in  the  solid  slate.  By  extracting  successively  with  weak, 
with  strong,  and  with  absolute  alcohol,  the  gluten-casein  of  Ritthausen, 
remains  undissolved. 

On  evaporating  the  alcoholic  solution  to  one-half,  there  separates,  011 
cooling,  a  brownish-yellow  mass.  This,  when  treated  with  absolute 
alcohol,  leaves  gluten-fibrin  nearly  pure. 

Vegetable  fibrin  is  readily  soluble  in  hot  dilute  alcohol, 
but  slightly  so  in  cold  dilute,  and  not  at  all  in  absolute  al- 
cohol. On  prolonged  heating  with  alcohol,  it  becomes  in- 
soluble in  that  liquid.  It  does  not  dissolve  in  water.  It 
has  no  fibrous  structure  like  animal  fibrin,  but  forms, 
when  dry,  a  tough,  horn-like  mass.  In  composition  it 
approaches  washed  muscle,  but  differs  considerably  from 
blood-fibrin. 

Wheat  contains  or  yields*  but  a  small  proportion  of 
fibrin  and  less  appears  to  exist  in  hard  than  in  the  soft 
wheats.  Eye  contains  less  than  wheat.  Barley,  from 
which  no  gluten  can  be  got,  yields  to  alcohol  a  small  pro- 
portion of  fibrin. 

Maize-fibrin,  Zein. — The  meal  of  Indian  corn,  unliko 
that  of  wheat  and  rye,  when  made  into  a  dough,  forma 
no  gluten,  but  it  yields  to  warm,  weak  alcohol  somo 
7  per  cent  of  fibrin  quite  similar  to  that  from  wheat, 
though  of  somewhat  different  composition. 


t  pre-exist  in  wheat 
od,  but  is  a  result  of 
ng  of  the  flour  to  a 

d<  ugh.  According  to  them  a  strong  solution  of  c  uumon  salt  extracts 
fr  )iii  wheat  flour  vegetable  globulin  (see  p.  !>7\  ai  d  the  residue,  when 
ki  eaded  with  water,  forms  no  gluten.  If,  however,  the  salt  solution  of 
gl  >bulin,  in  contact  with  the  flour,  is  largely  diluted  with  water,  the 
Hour  will  yield  gluten  by  kneading. 


*  Weyl  and  Bisehof  believe  that  gluten  does  nr 

,1  d  rye,  just  as  fibrin  does  not  exist  in  living  blc 

emical  change  during  the  wetting  and   knead 

ugh.     According  to  them  a  strong  solution  of  < 


94  HOW  CBOPS  GROW. 

Casein. — Animal  Casein  is  the  peculiar  albuminoid  of 
milk,  in  which  it  exists  dissolved  to  the  amount  usually 
of  3  to  6  per  cent.  By  saturating  milk  with  magnesium 
sulphate  the  casein  separates  as  an  opaque  white  precipi- 
tate. Thus  obtained  it  is  freely  soluble  in  water.  Casein 
is  also  precipitated  from  milk  by  adding  a  little  acetic  or 
other  acid,  but  is  then  nearly  insoluble  in  water,  has 
a  decided  acid  reaction,  and  reddens  blue  litmus.  The 
spontaneous  curdling  of  milk,  after  standing  at  or- 
dinary temperatures  for  some  time,  appears  to  be  directly 
due  to  the  lactic  acid  which  develops  from  milk-sugar  as 
the  milk  sours.  When  milk  is  swallowed  by  a  mamma- 
lian animal  it  curdles  directly,  and  in  the  making  of  cheese 
the  casein  of  milk  is  coagulated  by  the  use  of  rennet,  which 
is  an  infusion  of  tbe  membrane  lining  the  calf's  stomach. 
Coagulated  casein,  though  insoluble  in  water,  dissolves 
in  very  dilute  acids,  and  also  in  very  dilute  alkalies. 

The  coherent  cheese  curd  which  is  separated  from  milk 
by  rennet  is  doubtless  a  decomposition-product  of  casein, 
and  carries  with  it  a  considerable  portion  of  the  phosphates 
and  other  salts  of  the  milk.  These  salts  are  not  found  in 
the  casein  precipitated  by  acids,  being  kept  in  solution 
by  the  latter,  but  casein  appears  to  contain  a  small  amount 
of  phosphorus  (equivalent  to  0.9  per  cent  phosphoric 
oxide)  in  organic  combination.  Skim-milk  cheese,  when 
new,  consists  mainly  of  coagulated  casein  with  a  little 
fat.  Cheese  made  from  entire  milk  contains  most  of  the 
fat  of  the  milk. 

Exp.  50. — Observe  the  coagulation  of  casein  when  milk  is  treated 
with  a  few  drops  of  dilute  hydrochloric  acid.  Test  the  curd  with 
nitrate  of  mercury. 

EXP.  51.— Boil  milk  with  a  little  magnesium  sulphate  (Epsom  salts) 
•until  it  curdles. 

Vegetable  Casein. — Several  distinct  substances  have 
been  described  as  vegetable  caseins.  Our  knowledge  with 
regard  to  them  is  in  many  important  respects  very  defi- 
cient. Even  their  elementary  composition  is  a  matter  of 
uncertainty. 


THE  VOLATILE  PART  OF  PLANTS.  95 

Gluten- Casein. — That  part  of  the  gluten  of  wheat 
which  is  insoluble  in  cold  alcohol  is  digested  in  a  highly 
dilute  solution  of  potash,  and  the  clear  liquid  is  made 
faintly  acid  by  acetic  acid.  The  curdy  white  precipitate 
thus  obtained,  after  washing  with  water,  alcohol  and 
ether,  and  dried,  is  the  gluten-casein  of  Eitthausen.  It 
is  insoluble  in  water,  and  in  solutions  of  common  salt, 
easily  soluble  in  weak  alkalies  and  coagulated  by  acids. 
Eitthausen  obtained  this  body  from  wheat,  rye,  barley, 
and  buckwheat. 

Legumin  is  the  name  that  has  been  applied  to  the  chief 
albuminoid  of  oats,  peas,  beans,  lupins,  vetches,  and  other 
legumes.  It  is  extracted  from  the  pulverized  seeds  by 
dilute  alkalies,  and  is  thrown  down  from  these  solutions 
by  acids.  From  some  leguminous  seeds  it  may  be  partially 
extracted  by  pure  water,  probably  because  of  the  presence 
of  alkali-phosphates  which  serve  to  dissolve  it.  It  is 
generally  mixed  with  conglutin,  from  which  it  may  be 
separated  by  soaking  in  weak  brine  (a  5  per  cent  solution 
of  common  salt).  Thus  obtained,  it  is  insoluble  in  pure 
water  and  in  brine,  but  soluble  in  dilute  alkalies,  and  has 
a  decided  acid  reaction.  Legumin,  as  existing  in  the 
horse-bean  (  Viciafaba],  is  soluble  in  brine,  but  after  solu- 
tion in  alkali  and  precipitation  with  acids,  is  insoluble 
in  salt  solution.  The  casein,  animal  or  vegetable,  that 
is  thrown  down  from  salt-solution  by  acids  is  evidently  a 
chemical  compound  of  the  original  proteid  with  the  acid 
(acid-proteid). 

EXP.  52.— Prepare  a  solution  of  vegetable  casein  from  crushed  peas, 
almonds,  or  pea-nuts,  by  soaking  them  for  some  hours  in  warm  water, 
to  which  a  few  drops  of  dilute  ammonia-water  or  potash-lye  has  been 
added,  and  allowing  the  liquid  to  settle  clear.  Precipitate  the  casein 
by  addition  of  an  acid  to  the  solution. 

The  Chinese  are  said  to  prepare  a  vegetable  cheese  by 
boiling  peas  to  a  pap,  straining  the  liquor,  adding  gypsum 
until  coagulation  occurs,  and  treating  the  curd  thus  ob- 
tained in  the  same  manner  as  practiced  with  milk-cheese, 


96  SOW  CROPS  GKOW. 

viz.:  salting,  pressing,  and  keeping  until  f.he  odor  and 
taste  of  cheese  are  developed.  It  is  cheaply  sold  in  the 
streets  of  Canton  under  the  name  of  Tao-foo.  Vegetable 
casein  appears  to  occur  in  small  quantity  in  the  potato, 
and  many  plants  ;  and  may  be  exhibited  by  adding  a  few 
drops  of  acetic  acid  to  turnip  juice,  for  instance,  which 
has  been  freed  from  albumin  by  boiling  and  filtering. 

The  Globulins  are  insoluble  in  water,  but  dissolve  in 
neutral  salt-solutions.  Some  dissolve  only  in  salt-solu- 
tions of  moderate  strength  and  are  thrown  down  from 
these  solutions  by  more  salt.  Others  are  soluble  in  sat- 
urated salt-solutions.  They  are  coagulated  by  heat. 
Some  animal  globulins  may  first  be  noticed. 

Vitellin  is  obtained  from  the  yolk  of  eggs  ;  fat  and 
pigment  are  first  removed  by  ether,  and  the  white  residue 
is  dissolved  in  a  solution  of  common  salt  (1  of  salt  to  10 
of  water).  Addition  of  water  to  the  filtered  solution 
separates  the  vitellin  as  a  white,  flocky  mass. 

Paraglobulin  exists  in  blood  serum,  and  may  be 
thrown  down  by  saturating  the  serum  with  magnesium 
sulphate.  It  may  be  obtained  in  transparent  microscopic 
disks  that  are  probably  crystalline.  Its  solutions  in  brine 
coagulate  by  heat,  like  albumin. 

Fibrinogen. — When  blood  fresh  from  the  veins  of  the 
horse  is  mixed  directly  with  a  saturated  aqueous  solution 
of  magnesium  sulphate,  fibrinogen  dissolves,  and  the 
liquid,  after  filtering  from  the  red  corpuscles,  upon  mix- 
ing with  a  saturated  brine  of  common  salt,  deposits  this 
body  in  white  flocks,  which  unite  to  a  tough,  elastic 
mass.  Its  solutions  in  brine  coagulate  at  a  lower  tem- 
perature than  those  of  paraglobulin. 

Fresh-drawn  blood,  after  standing  a  short  time,  coag- 
ulates of  itself  to  a  more  or  less  firm  clot.  Under  the 
microscope  this  process  is  seen  to  consist  in  the  rapid 
formation  of  an  intricate  net-work  of  delicate  threads  or 
fibrils.  These  are  fibrin,  and  come  from  the  coagulation 


THE  VOLATILE  PART  OF  PLANTS.  97 

of  fibrinogen.  Coagulation  here  appears  to  be  induced 
by  a  ferment  whose  effect  is  suspended  by  strong  saline 
solutions,  but  is  renewed  when  these  are  mixed  with 
much  water.  This  ferment  occasions  decomposition  of 
the  fibrinogen,  fibrin  being  one  of  the  products.  The 
fibrin-ferment  is  supplied  from  ruptured  white  blood- 
corpuscles.  The  chemical  composition  of  fibrinogen  and 
fibrin,  as  determined  by  analysis,  is  quite  the  same. 

Myosin. — Lean  beef  or  other  dead  muscle-tissue,  after 
mincing  and  washing  with  water  to  remove  coloring  mat- 
ters, is  soaked  in  10  per  cent  salt-solution.  Myosin  dis- 
solves and  is  precipitated  from  the  filtered  brine  by  diluting 
with  water.  It  dissolves  also  in  dilute  hydrochloric  acid 
and  in  dilute  potash  solution.  Strong  hydrochloric  acid 
converts  it  into  syntonin.  Myosin  does  not  exist  in  liv- 
ing muscle,  but  is  formed  after  death,  during  rigor  mor- 
tis, from  the  juices  of  the  muscles  by  a  process  of  coag- 
ulation. Its  formation  is  accompanied  by  the  develop- 
ment of  lactic  and  carbonic  acids.  Myosin  is  the  chief 
ingredient  of  what  was  formerly  known  as  muscle-fibrin. 

Vegetable  Globulins  occur  abundantly  in  seeds  where 
they  are  chief  ingredients  of  the  so-called  aleurone  or 
protein-granules.  From  these  protein-granules,  or  from 
the  pulverized  seeds,  the  globulins  are  extracted  by  salt- 
solutions  and  by  weak  alkalies.  The  globulin  which 
water  alone  extracts  from  many  seeds  is  dissolved  by  help 
of  the  salts,  which  are  there  present.  Such  saline  ex- 
tracts are  coagulated  by  heat  and  thus  globulins  have 
figured,  no  doubt,  as  ''vegetable  albumin."  Some  glob- 
ulins are  only  known  in  the  amorphous  or  granular  state  ; 
others  occur  as  crystals. 

Conglutin  exists  abundantly,  according  to  Eitthausen, 
in  the  seeds  of  peach,  almond,  lupin,  radish,  pea-nut, 
hickory-nut,  and  hazel-nut,  where  it  is  usually  associated 
with  legumin.  It  may  be  separated  by  weak  brine,  in 
which  it  is  invariably  soluble,  while  legumin,  after  sepa- 
7 


98  HOW  CROPS  GROW. 

ration  from  alkali-solutions,  is  undissolved  by  brine.  The 
conglutin  obtained  from  lupins  and  pea-nuts  differs  some- 
what from  that  found  in  the  hazel-nut,  and  in  almond 
and  peach  seeds.  Conglutin  cannot  be  crystallized  from 
salt-solutions,  as  readily  happens  with  vegetable  vitellin. 

Vegetable  Vitellin. — Applying  this  designation  to  al- 
buminoids which  are  insoluble  in  water,  but  dissolve  in 
saturated  salt-solutions,  and  are  thence  precipitated  by 
water,  we  find  vitellin  more  or  less  abundantly  in  seeds 
of  squash,  hemp,  sunflower,  lupin,  bean,  pea,  Brazil-nut, 
castor-bean,  and  various  other  plants.  It  may  be  extracted 
from  squash  seeds  by  common-salt-solution  (of  10  per 
cent)  or  dilute  alkali.  Diluting  the  brine  with  water  or 
neutralizing  the  alkali  with  acids  precipitates  the  vitellin, 
which,  after  washing  with  water,  alcohol  and  ether,  may 
be  obtained  in  crystals  (microscopic  octahedrons)  by  dis- 
solving in  warm  brine  and  slowly  cooling.  From  seeds 
of  hemp  and  castor-bean  Ritthausen  obtained  crystals 
identical  in  appearance  and  composition  with  those  of 
squash  seeds,  but  soluble  in  water,  probably  because  of 
the  presence  of  alkali  salts. 

Vegetable  Myosin. — Weyl  and  Bischof  consider  that 
cereal  and  leguminous  seeds  contain  or  yield  myosin  anal- 
ogous to  muscle-myosin,  which  differs  from  vitellin  (and 
conglutin)  in  being  precipitated  from  its  solution  in  weak 
brine  by  saturating  the  same  with  salt.  They  find  that 
wheat-flour  contains  but  little  if  any  proteid  besides 
myosin,  and  that  when  this  is  removed  from  the  flour  by 
salt-solution  or  by  very  weak  soda-lye  or  by  hydrochloric 
acid  of  0.1%,  the  residue  is  incapable  of  yielding  gluten. 
Gluten  is  therefore  a  decomposition-product  of  myosin. 
These  results  are  confirmed  by  the  recent  work  of  Mar- 
tin (Jour,  of  Physiology,  1887).  Zoeller  found  that  the 
pulp  of  potatoes,  after  starch  and  soluble  matters  had 
been  removed  by  copious  washings,  with  water,  yielded  to 
salt-solution  an  albuminoid  which  separated  when  thi 


THE  VOLATILE  PART  OF  PLANTS.         99 

brine  was  saturated  by  addition  of  salt  in  excess.  He  also 
precipitated  myosin  from  the  juice  of  the  tubers  by  sat- 
urating it  with  salt. 

The  myosins  are  precipitated  by  conversion  into  alkali- 
proteids,  when  their  brine-solutions  are  deprived  of  salt 
by  dialysis  or  when  these  solutions  are  kept  for  some 
hours  at  100°  F.  (Sidney  Martin. ) 

Vegetable  Paraglobulin  is  recently  stated  to  exist  in 
papaw-juice,  and  in  the  seeds  of  lequirity,  Abrus  preca- 
torius.  It  is  distinguished  from  myosin  by  requiring  a 
higher  temperature  for  coagulation  from  salt-solutions 
and  in  not  suffering  conversion  into  an  insoluble  alkali- 
proteid  by  dialysis  or  long  heating  to  100°  F.  (Martin.) 

Acid-Proteids  are  bodies  formed  from  proteids  by  the 
prolonged  action  of  acids.  They  are  insoluble  in  water, 
alcohol  and  brines,  but  easily  soluble  in  dilute  acids  or 
alkalies,  and  are  precipitated  by  neutralizing  these  solu- 
tions. The  solutions  of  acid-proteids  in  acids  are  not  co- 
agulable  by  heat.  The  albumins  and  globulins  are  grad- 
ually converted  into  acid-proteids  by  cold,  highly  dilute 
acids,  and  more  rapidly  by  stronger  acids  and  gentle  heat. 
Syntonin  is  the  acid-proteid  resulting  from  solution  of 
muscle-flesh,  or  myosin,  in  weak  hydrochloric  acid,  and  is 
thrown  down  when  the  solution  is  neutralized  by  an 
alkali,  as  a  white  gelatinous  substance.  Acid-proteids 
may  exist  in  seeds  such  as  the  oat,  lupin,  pea,  bean,  etc., 
which  contain  so  much  free  acid,  or  acid  salt,  that  the 
water  extract  is  strongly  acid  to  test-papers. 

Alkali-Proteids,  or  Albuminates. — The  action  of 
dilute  alkali-solutions  on  most  proteids  converts  them 
into  bodies  which,  like  acid-proteids,  are  insoluble  in 
water  and  salt-solutions,  but  soluble  in  dilute  acids  and 
alkalies,  and  are  thrown  down  from  these  solutions  by 
neutralization.  Dilute  acids  do  not  convert  them  into 
acid-proteids.  Alkali-proteids  are  said  to  exist  gener- 
ally in  the  young  cells  of  the  animal,  and  may  also  occur 


100  SOW  CROPS  GROW. 

in  plants  in  the  alkaline  juices  of  tlie  cambium.  The 
"vegetable  caseins,"  viz.,  legumin  and  gluten-casein,  as 
they  occur  in  the  alkaline  juices  or  extracts  of  plants, 
are  probably  bodies  of  this  class,  and  when  precipitated  by 
acids  unite  to  the  latter,  forming  compounds  with  an 
acid  reaction.  Casein  of  milk  has  been  by  some  consid- 
ered to  be  an  alkali-proteid,  but  is  probably  distinct. 

Proteoses  and  Peptones. — These  terms  designate 
bodies  that  result  from  the  chemical  alteration  of  albu- 
minoids, under  the  influence  of  "ferments"  which  exist 
in  plants,  but  which  have  been  most  fully  studied  as  they 
occur  in  the  digestive  apparatus  of  animals. 

The  albuminoids,  as  found  in  plants,  are  mostly  insol- 
uble in  the  vegetable  juices,  and  those  which  are  soluble 
(probably  because  of  the  presence  of  salts,  acids  or  alka- 
lies) are  mostly  incapable  of  freely  penetrating  the  cell- 
membranes  which  inclose  them,  and  cannot  circulate  in  the 
vegetable  juices,  and  likewise,  when  they  become  the  food 
of  animals,  cannot  leave  the  alimentary  canal  so  as  to  be- 
come incorporated  with  the  blood  until  they  have  been 
chemically  changed.  During  the  processes  of  animal 
digestion  the  albuminoids  of  whatever  kind  undergo  solu- 
tion and  conversion  into  bodies  which  are  freely  soluble 
in  water,  and  rapidly  penetrate  the  moist  membranes  of 
the  intestines,  and  thus  enter  into  the  circulation.  These 
bodies  have  been  prepared  for  purposes  of  study  by  a 
partly  artificial  digestion,  carried  on  in  glass  vessels  with 
help  of  the  digestive  ferments  obtained  from  the  stomach 
(pepsin)  or  pancreas  (trypsin)  of  animals.* 

It  appears  from  Kuhne  and  Chittenden's  investigations 
that  a  series  of  soluble  and  diffusible  products  are  formed 
from  each  albuminoid  with  progressive  diminution  of 
carbon  and  increase  of  oxygen,  and,  in  some  cases,  of 
nitrogen.  The  first-formed  products  are  termed  pro- 

*  Reference  may  be  had  to  Chittenden's  Studies  in  Physiological 
Chemistry,  Connecticut  Acad.,  Vols.  II  and  111,  1887  and  1889. 


THE  VOLATILE  PAKT  OF  PLANTS.  161 

teoses  (albumoses,  caseoses,  globuloses,  etc.) ;  those  last 
produced  they  designate  peptones,  but  investigators  are 
not  as  yet  agreed  as  to  the  precise  application  of  these 
terms.  What  have  been  formerly  called  peptones  are 
now  considered  to  be  largely  proteoses. 

The  composition  of  some  of  these  bodies  may  be  seen 
from  the  following  analyses  by  Chittenden  and  Painter  : 
c.  H.          N.  s.          o. 

Casein 53.30  7.07  15.91  0.82  22.03 

Protocaseose 52.50  7.15  15.73  0.96  23.86 

Deuterocaseose 51.59  6.98  15.73  0.75  25.03 

Casein-Peptone 49.94  6.51  16.30  0.68  26.57 

Of  the  several  products  which  have  been  analyzed  and 
classed  as  proteoses  and  peptones,  it  is  not  certain  that 
any  one  is  a  strictly  homogeneous  substance.  It  is  more 
than  probable  that  some  of  them  are  mixtures.  The 
proper  use  of  these  names  is  provisional,  to  characterize 
certain  evidently  distinct  stages  of  albuminoid  metamor- 
phosis, whose  exact  nature  can  only  be  cleared  up  by 
further  investigation. 

The  peptones  may  be  defined  as  the  final  products  of 
the  action  of  the  peptic  ferment.  They  are  soluble  in 
water  and  freely  diffusible  through  animal  membranes. 
The  albumoses  (or  proteoses)  are  intermediate  between 
the  albuminoids  and  the  peptones,  being  mostly  soluble 
in  water  but  not  freely  diffusible. 

The  proteoses  much  resemble  the  albuminoids  from 
which  they  are  derived,  not  only  in  composition,  but  iu 
many  of  their  properties.  The  peptones  have  less  re- 
semblance, but  appear  capable  of  partially  reverting  to 
proteoses,  as  some  of  the  latter  are  said  to  yield  coagula- 
ble  albuminoids  when  kept  in  the  moist  state. 

Weak  acids  and  alkalies  also  convert  the  albuminoids 
into  proteoses  and  peptones,  and  probably  the  acid-pro- 
teids,  perhaps  also  the  alkali-proteids,  already  mentioned, 
contain  proteoses  in  admixture.  Since  pepsin-digestion 
requires  the  aid  of  a  free  acid  and  trypsin-digestion  sue- 


102  HOW  CROPS  GROW. 

ceeds  best  in  presence  of  a  free  alkali,  the  conditions 
under  which  the  proteoses  of  digestion  are  formed  are  in 
part  identical  with  those  that  give  rise  to  the  acid-pro- 
teids  and  alkali-proteids. 

Peptones  have  been  found  in  small  proportions  in  the 
ivater-extract  of  various  plants,  e.  g.,  seedlings,  lupins, 
barley-malt,  young  grass,  alfalfa,  etc.  (Vs.  St.,  XXIV, 
363,  371,  440,  and  XXXII,  389.) 

Vines  has  found  a  proteose  in  considerable  quantity  in 
the  seeds  of  lupin,  peony,  and  wheat  and  in  the  Brazil- 
nut  and  castor-bean,  and  considers  bodies  of  this  class  to 
be  of  general  occurrence  in  the  protein-granules  of  plants. 

The  proteose  (hemialbumose*)  from  lupins  has,  exclu- 
sive of  0.81  p.  c.  of  ash,  the  following  composition  per 
cent  according  to  Vines  : 

c.          H.          N.          s.          o. 

52.58  7.24  14.87  1.52  23.79 

Sidney  Martin  reports  the  existence  of  a  proteose 
(hemialbumose)  in  the  juice  of  the  papaw  or  melon 
tree  (Carica  papaya)  where  it  is  associated  with  the  fer- 
ment papain,  which  is  very  similar  to  that  of  the  pan- 
creatic secretion  of  animals. 

Ferments  are  substances  which  produce  or  excite 
chemical  changes  in  a  manner  as  yet  mostly  unexplained, 
the  ferments  themselves  not  appreciably  contributing  of 
their  own  substance  to  the  products  of  the  processes 
which  they  set  in  operation. 

The  ferments  that  figure  in  agricultural  chemistry  are 
closely  related  to  and  apparently  derived  from  the  albu- 
minoids, but  in  no  case  has  their  chemical  composition 
been  positively  established.  They  are  distinguished  and 
characterized  almost  solely  by  the  sources  whence  they 
are  derived,  and  the  effects  which  they  produce.  The 

•Kiihne  first  distinguished  the  products  of  pepsin  or  trypsin  diges- 
tion into  hemialbumose  and  antialbumose,  the  former  being  converted 
by  trypsin  into  amido-acids  (see  p.  114),  the  latter  remaining  unaltered 
by  the  digestive  ferments.  KUhne  &  Chittendon  have  more  recently 
shown  "  hemialbumose  "  to  be  a  mixture  mainly  of  proto  and  dentero- 
albumose. 


THE  VOLATILE   PART   OF   PLANTS.  103 

substances  which  the  chemist  can  prepare,  and  to  which 
he  gives  special  designations,  are  doubtless  mixtures,  and 
in  most  cases  contain  but  a  small  proportion  of  the  real 
ferment,  which,  in  a  state  of  entire  purity,  is  unknown. 

Leaven,  or  Yeast,  which  has  been  employed  in  mak- 
ing bread,  wine  and  beer  for  many  centuries,  contains,  or 
mainly  consists  of,  a  microscopic  plant  of  very  simple 
structure  (pp.  244-5),  which,  when  placed  in  a  solution  of 
cane-sugar,  is  able  in  the  first  place  to  cause  the  "inver- 
sion "  of  that  substance  into  the  two  sugars,  dextrose  and 
levulose,  and,  secondly,  to  transform  both  the  latter  into 
alcohol  and  carbon  dioxide.  The  "  inverting  "  effect  of 
yeast  upon  cane-sugar  has  been  traced  to  a  substance 
which  can  be  separated  from  the  yeast  and  obtained  as  a 
dry,  white  powder.  The  alcoholic  fermentation  requires 
the  living  yeast  plant  for  its  accomplishment.  Ferments 
are  accordingly  divided  into  the  two  classes,  unorganized 
and  organized.  We  shall  here  notice  briefly  a  few  unor- 
ganized ferments  or  enzymes,  as  they  are  also  termed, 
that  have  been  somewhat  carefully  studied. 

Invertin  is  obtained  from  dry,  pulverized  yeast  by 
heating  it  to  212°  to  coagulate  albumin  and  then  ex- 
tracting with  warm  water.  The  invertin  dissolves,  and, 
by  addition  of  alcohol,  is  precipitated.  Barth  thus  ob- 
tained a  substance  containing  6  per  cent  of  nitrogen 
which  was  able,  in  the  course  of  48  hours,  to  transform 
(invert)  760  times  its  weight  of  cane-sugar.  Invertin 
has  no  effect  on  starch  or  dextrin. 

Diastase  is  the  name  applied  to  a  substance  that  may  be 
obtained  as  a  whitish  powder  from  sprouted  barley  (malt) 
by  extracting  with  dilute  alcohol  and  precipitation  with 
strong  alcohol,  which  is  capable  of  transforming  2,000 
times  its  weight  of  starch,  first  into  dextrin  and  finally 
into  maltose  and  dextrose.  The  purest  diastase  prepared 
by  Lintner  contained  10.4  per  cent,  nitrogen  and  gave 
reactions  for  albuminoids,  but  it  had  properties  besides 


104  HOW  CROPS  GROW. 

its  action  on  starch  that  strikingly  distinguished  it  from 
the  ordinary  proteids. 

Pepsin  is  that  ferment  of  the  so-called  gastric  juice  of 
the  animal  stomach  which  enables  this  organ  to  dissolve 
and  "peptonize"  the  albuminoids  of  the  food.  It  may 
be  extracted  from  the  inner  coating  of  the  stomach  by 
glycerine  or  very  dilute  hydrochloric  acid,  and  is  precip- 
itable  from  these  solutions  by  strong  alcohol.  Pepsin 
requires  the  presence  of  a  free  acid  to  dissolve  the  albu- 
minoids ;  in  neutral  or  alkaline  solution  it  has  no  "di- 
gestive power." 

Trypsin  is  a  ferment  formed  in  the  pancreas  and  exist- 
ing in  the  pancreatic  juice  which,  in  mammalian  animals, 
during  the  digestion  of  food,  is  poured  into  the  upper 
intestine,  where  it  continues  and  completes  the  solution 
of  albuminoids  begun  by  the  gastric  juice.  Trypsin  acts 
jn  neutral  but  most  effectively  in  alkaline  solutions  ;  its 
operation  is  arrested  by  free  acids.  The  results  of  its 
action  differ  in  some  respects  from  those  of  pepsin. 

Papain. — The  milky  juice  of  the  Brazilian  plant  Car- 
tea  papaya,  or  melon-tree,  contains  this  ferment,  which, 
like  trypsin,  is  freely  soluble  in  water,  rapidly  dissolves 
albuminoids,  best  in  neutral  or  alkaline  solutions,  convert- 
ing them  into  proteoses  and  peptones.  Papain  itself,  as 
obtained  by  Wurtz  &  Bouchut,  has  the  properties  and 
composition  that  characterize  the  proteoses. 

Ferments  appear  to  perform  very  important  functions 
in  the  vegetable  as  well  as  in  the  animal  organism,  and 
have  to  be  referred  to  frequently  as  occasioning  the  con- 
version of  insoluble  into  soluble  substances,  and  of  com- 
plex into  simpler  bodies. 

Composition  of  the  Albuminoids. — There  are  va- 
rious reasons  why  the  exact  composition  of  some  of  the 
bodies  just  described  is  still  a  subject  of  uncertainty.  They 
are,  in  the  first  place,  naturally  mixed  or  associated  with 
other  matters  from  which  it  is  very  difficult  to  separate 


THE  VOLATILE   PART  OF  PLANTS.  105 

them  fully.  Again,  if  we  succeed  in  removing  foreign 
substances,  it  must  usually  be  done  by  the  aid  of  acids, 
alkalies,  salt-solutions,  alcohol  and  ether,  and  there  is 
reason  to  believe  that  in  many  cases  these  reagents  essen- 
tially modify  the  properties  and  composition  of  the  pro- 
teids.  These  bodies,  in  fact,  as  a  class,  are  extremely 
susceptible  to  change  and  alter  in  respect  to  appearance, 
solubility,  and  other  qualities  that  serve  to  distinguish 
them,  without  any  corresponding  change  in  chemical 
composition  being  discoverable  by  our  methods  of  anal- 
ysis. On  the  other  hand,  the  substances  that  have  been 
prepared  by  different  experimenters  from  the  same 
sources,  and  by  substantially  the  same  methods,  often 
show  decided  differences  of  composition. 

Finally,  the  methods  of  analysis  used  in  determin- 
ing their  composition  are  liable  to  considerable  error, 
and,  if  applied  to  the  pure  substances,  are  scarcely 
delicate  enough  to  indicate  their  differences  with  entire 
accuracy. 

In  the  accompanying  table  (p.  106)  are  given  the  most 
recent  and  trustworthy  analyses  of  the  various  vegetable 
albuminoids,  and  of  the  corresponding  substances  of  ani- 
mal origin. 

Referring  to  the  analyses  of  Albumins  we  observe  that 
the  egg-albumin  differs  from  serum-albumin  in  contain- 
ing about  one  per  cent  more  of  oxygen  and  one  less  of 
carbon,  while  hydrogen,  nitrogen  and  sulphur  are  prac- 
tically the  same.  These  two  albumins  have  been  very 
thoroughly  studied,  their  difference  of  composition  is 
well  established,  and  they  have  positive  differences  in 
their  properties,  so  that  there  can  be  little  doubt  that 
they  are  specifically  distinct  substances.  Of  the  Vegeta- 
ble Albumins  none  offer  any  reasonable  guarantee  of 
purity.  The  composition  of  barley-albumin  is  near  that 
of  the  animal  albumins,  but  it  contains  one-third  less 
sulphur.  So  far,  then,  as  present  data  indicate,  the  veg- 


106 


HOW   CEOPS   GROW. 


COMPOSITION  OF  ALBUMINOIDS. 


ALBUMINS. 


Egg 

Blood  serum. 

Wheat 

Barley 


FIBRINS. 


Blood  

Gluten-fibrin,  wheat. 
"          "       maize . 

CASEINS. 


52.2 
53.1 
53.1 
52. 


87 


6.9  15.8  1.923.2 
.9  16. Oil. 8  22. 2 

7.217.61.620.5 
.215.81.223.0 


.  7  6 


62 

54 
54.67.5l5.50.721,7 


.3  7 


Milk  casein  * 

Gluten-casein,  wheat 152. £ 

"       62. 

Gluten-casein,  buckwheat*.  50. 
Legumin,  lupins 51. 


GLOBULINS. 


Paraglobulin 52. 

Fibrinogen,  blood 52. 

Myosin,  beef 152. 

Conglutin,  lupin 50 . 1 

hazel-nut 

Vitellin,  squash 

"       hemp  (crystals) 

"       Brazil-nut 


51.2 

51. 

61. 

52. 


GLIADIN,  wheat . 


Analysts. 

Chittenden  &  Polton. 
Hammarsten. 

•  Ritthausen. 


8116.9  1.1122.  5     Hammarsten. 

2  16.9  1.0(20.6  )  T>mhall<,pn 
Rlttnausen. 


!)7.f 
87 


47 


53.37.1  15.90.822.0 
017.11.022.0 
015.811.123.3 
817.4'1.524.1 
017.50.623.5 


Chittenden  &  Painter. 
Ritthausen. 
Chittenden  &  Smith. 

I  Ritthausen. 


Hammarsten. 


77.015.81.123.4 
96.916.71.322.2 
8  7. 1 '  16. 8  1.31 21. 9  Chittenden  &  Cummins. 

7.0,18.71.123.0  1 


47 


.5  18. 

.0,18.70.8  22.5!  I 
.118.10.521.9i     Weyl. 


52.77.1  18.00.921.3 


Ritthausen. 


MUCEDIN,  wheat 54.1  6.9  16.6  0.9  21.5     Ritthausen. 

See  pp.  101  and  102  for  analyses  of  Proteoses  and  Peptone. 

etable  albumins  are  not  identical  with  those  derived  from 
the  animal. 

As  respects  the  Fibrins  we  have  already  seen  that  there 
is  no  similarity  in  properties  between  that  of  blood  and 
those  obtained  from  gluten.  The  analyses  of  the  two 
gluten-fibrins  show  either  that  these  substances  are  quite 
distinct  or  that  they  have  not  yet  been  obtained  in  the 
pure  state. 

The  Vegetable  Caseins,  as  analyzed  by  Ritthausen,  are 

*  The  analysis  of  milk  casein  should  include  0.9  phosphorus.  The 
buckwheat  casein  contained  0.9  phosphorus,  which  is  not  included  in 
the  analysis.  Whether  phosphorus  is  an  ingredient  of  casein,  or  an 
"  impurity,"  is  ivot  perhaps  positively  established. 


THE  VOLATILE  PART  OF  PLANTS.  107 

observed  to  contain  more  nitrogen  by  1.2  to  1.6  per  cent 
than  exists  in  animal  casein.  Furthermore,  they  differ 
from  each  other  so  widely  in  carbon  content  (2.7  percent) 
as  to  make  it  highly  probable  that  their  true  composition 
was  not  in  all  cases  correctly  determined. 

This  conclusion  is  justified  by  the  results  of  Chittenden 
&  Smith,  who  have  recently  analyzed  five  different  prep- 
arations of  gluten-casein,  made  from  wheat  by  Eitthau- 
sen's  method.  The  average  of  their  accordant  analyses 
is  given  above.*  Since  nitrogen  was  determined  by  two 
methods  (those  of  Dumas  and  Kjeldahl)  these  analyses 
would  appear  to  establish  the  composition  of  gluten- 
casein,  which  accordingly  closely  agrees  with  that  found 
by  Ritthausen  for  "  albumin "  from  barley,  and  with 
that  of  paraglobulin,  and  has  the  same  nitrogen  content 
as  the  casein  of  milk. 

The  Animal  Globulins  agree  in  composition  with  each 
other  as  well  as  with  animal  fibrin  which  is  formed  from 
globulin  (fibrinogen).  The  Vegetable  Globulins  are  strik- 
ingly different  in  composition,  containing  1.5  to  2  per 
cent  more  nitrogen  and  mostly  but  half  as  much  sul- 
phur. The  hazel-nut  conglutin  and  the  hemp-seed  vitel- 
lin  have  the  same  composition. 

It  is  evident  that  the  vegetable  albuminoids,  on  the 
whole,  are  distinct  from  those  of  the  animal,  but  their 
true  composition  and  relations  to  each  other,  to  a  great 
extent,  remain  to  be  established. 

Some  Mutual  Relations  of  the  Albuminoids. — It  was 
formerly  supposed  that  these  bodies  are  identical  in  com- 
position, the  differences  among  the  analytical  results 
being  due  to  foreign  matters,  and  that  they  differ  from 
each  other  in  the  same  way  that  cellulose  and  starch 
differ,  viz. :  on  account  of  different  arrangement  of  the 
atoms.  Afterwards,  Mulder  advanced  the  notion  that 
the  albuminoids  are  compounds  of  various  proportions 

*  Kindly  communicated  by  the  authors. 


108  HOW   CROPS   QKOW. 

of  hypothetical  sulphur  and  phosphorus  radicles  with 
a  common  ingredient,  which  he  termed  protein  ^from 
the  Greek  signifying  "  to  take  the  first  place,"  because 
of  the  great  physiological  importance  of  such  a  body). 
Hence  the  designations  protein-bodies  and  proteids. 
The  transformations  which  these  substances  are  capable 
of  undergoing  sufficiently  show  that  they  are  closely 
related,  without,  however,  satisfactorily  indicating  in 
what  manner. 

In  the  animal  organism,  the  albuminoids  of  the  food, 
of  whatever  name,  are  dissolved  in  the  juices  of  the 
digestive  organs,  and  pass  into  the  blood,  where  they 
form  blood  albumin  and  globulin.  As  the  blood  nour- 
ishes the  muscles,  they  are  modified  into  the  flesh-albu- 
minoids ;  on  entering  the  mammary  system  they  are 
converted  into  casein,  while  in  the  appropriate  part  of 
the  circulation  they  are  formed  into  the  albumin  of  the 
egg,  or  embryo. 

In  the  living  plant,  similar  changes  of  place  and  of 
character  occur  among  these  substances. 

The  Albuminoids  in  Animal  Nutrition. — We  step 
aside  for  a  moment  from  our  proper  plan  to  direct  atten- 
tion to  the  beautiful  adaptation  of  this  group  of  organic 
substances  to  the  nutrition  of  animals.  Those  bodies 
which  we  have  just  noticed  as  the  animal  albuminoids, 
together  with  others  of  similar  composition,  constitute 
a  large  share  of  the  healthy  animal  organism,  and  espec- 
ially characterize  its  actual  working  machinery,  being 
essential  ingredients  of  the  muscles  and  cartilages,  as 
well  as  of  the  nerves  and  brain.  They  likewise  exist 
largely  in  the  nutritive  fluids  of  the  animal — in  blood 
and  milk.  So  far  as  we  know,  the  animal  body  has  not 
the  power  to  produce  a  particle  of  albumin,  or  fibrin,  or 
casein  except  by  the  transformation  of  similar  bodies  pre- 
sented to  it  from  external  sources.  They  are  hence  indis- 
pensable ingredients  of  the  food  of  animals,  and  were 


THE  VOLATILE   PAET  OF   PLANTS.  109 

therefore  designated  by  Liebig  as  the  plastic  elements  of 
nutrition.  They  have  also  been  termed  the  blood-build- 
ing or  muscle-forming  elements.  It  is,  in  all  cases,  the 
plant  which  originally  constructs  these  substances,  and 
places  them  at  the  disposal  of  the  animal. 

The  albuminoids  are  mostly  capable  of  existing  in  the 
liquid  or  soluble  state,  and  thus  admit  of  distribution 
throughout  the  entire  animal  body,  as  in  blood,  etc.  They 
likewise  readily  assume  the  solid  condition,  thus  becom- 
ing more  permanent  parts  of  the  living  organism,  as  well 
as  capable  of  indefinite  preservation  for  food  in  the  seeds 
and  other  edible  parts  of  plants. 

Complexity  of  Constitution. — The  albuminoids  are 
highly  complex  in  their  chemical  constitution.  This  fact 
is  shown  as  well  by  the  multiplicity  of  substances  which 
may  be  produced  from  them  by  destructive  and  decom- 
posing processes  as  by  the  ease  with  which  they  are 
broken  up  into  other  and  simpler  compounds.  Kept  in 
the  dissolved  or  moist  state,  exposed  to  warm  air,  they 
speedily  decompose  or  putrefy,  yielding  a  large  variety  of 
products.  Heated  with  acids,  alkalies,  and  oxidizing 
agents,  they  mostly  give  origin  to  the  same  or  to  anal- 
ogous products,  among  which  no  less  than  twenty  differ- 
ent compounds  have  been  distinguished. 

The  numbers  of  atoms  that  are  associated  in  the  mole- 
cules of  the  proteids  are  very  great,  though  not  in  most 
cases  even  approximately  known.  The  Haemoglobin  of 
blood,  which  forms  red  crystals  that  admit  of  preparing 
in  a  state  of  great  purity,  contains  in  100  parts — 

C  H  N  O  S  Fe 

54.2  7.2  16.1  21.6  0.5  0.4 

The  iron  (Fe)  is  a  constant  and  essential  ingredient,  and 
if  one  atom  only  of  this  metal  exist  in  the  haemoglobin 
molecule,  its  empirical  formula  must  be  something  like 
Ce4oHioooN"iMFeS3Oi9o,  and  its  molecular  weight  over  14,- 
000.  Haemoglobin  readily  breaks  up  into  a  proteid  and  a 


110 


HOW  CROPS  GROW. 


much  simpler  red  crystalline  substance,  Haemaeetin,  yield- 
ing about  96  per  cent  of  the  former  and  4  per  cent  of 
the  latter.  Haematin  has  approximately  the  formula 
CssHaiNiFeOs,  so  that  the  proteid,  though  simpler  than 
haemoglobin,  must  have  an  extremely  complicated  mole- 
cule, and  it  is,  accordingly,  difficult  to  decide  whether  a 
few  thousandths  of  the  acids,  bases  or  salts  which  may 
be  associated  with  these  bodies,  as  they  exist  in  plants  or 
pass  through  the  hands  of  the  chemist,  are  accidental  or 
essential  to  their  constitution. 

Occurrence  in  Plants. — Aleurone. — It  is  only  in  the 
old  and  virtually  dead  parts  of  a  living  plant  that  albu- 
minoids are  ever  wanting.  In  the  young  and  growing 
organs  they  are  abundant,  and  exist  dissolved  in  the  sap 
or  juices.  They  are  especially  abundant  in  seeds,  and 
here  they  are  often  deposited  in  an  organized  form,  chiefly 


ooooa 


Fig.  18.  Fig.  19. 

in  grains  similar  to  those  of  starch,  and  mostly  insoluble 
in  water. 

These  grains  of  albuminoid  matter  are  not,  in  many 
cases  at  least,  pure  albuminoids.  Hartig,  who  first  de- 
scribed them  minutely,  has  distinguished  them  by  the 
name  aleurone,  a  term  which  we  may  conveniently  em- 
ploy. By  the  word  aleurone  is  not  meant  simply  an 


THE  VOLATILE  PAKT  OF  PLANTS. 


Ill 


albuminoid,  or  mixture  of  albuminoids,  but  the  organ- 
ized granules  found  in  the  plant,  of  which  the  albumin- 
oids are  chief  or  characteristic  ingredients. 

In  Fig.  18  is  represented  a  magnified  slice  through  the 
outer  cells  (bran)  of  a  husked  oat  kernel.  The  cavities 
of  these  outer  cells,  a,  c,  are  chiefly  occupied  with  very 
fine  grains  of  aleurone.  In  one  cell,  b,  are  seen  the 
much  larger  starch  grains.  In  the  interior  of  the  oat 
kernel,  and  other  cereal  seeds,  the  cells  are  chiefly  occu- 
pied with  starch,  but  throughout  grains  of  aleurone  are 
more  or  less  intermingled. 

Fig.  19  exhibits  a  section  of  the  exterior  part  of  a 
flax-seed.  The  outer  cells,  a,  contain  vegetable  muci- 
lage ;  the  interior  cells,  e,  are  mostly  filled  with  minute 
grains  of  aleurone,  among  which  droplets  of  oil,  /,  are 
distributed. 

In  Fig.  20  are 
shown  some  of  the 
forms  assumed  by  in- 
dividual  albuminoid- 
grains  ;  a  is  aleurone 
from  the  seed  of  the  vetch,  J  from  the  castor-bean,  c 
from  flax-seed,  d  from  the  fruit  of  the  bayberry  (Myrica 
cerifera)  and  e  from  mace  (an  appendage  to  the  nutmeg, 
or  fruit  of  the  Myristica  moscliatd). 

Crystalloid  aleurone. — It  has  been  already  remarked 


c 

Fig.  20. 


Fig.  21. 

that  crystallized  albuminoids  exist  in  plants.     This  was 
first  observed  by  Hartig   (Entwickelungsgeschichte  des 


112  HOW  CHOPS  GEOW. 

PflanzenTceims,  p.  104).  In  form  they  sometimes  imitate 
crystals  quite  perfectly,  Fig.  21,  a;  in  other  cases,  5, 
they  are  rounded  masses,  having  some  crystalline  planes 
or  facets.  They  are  soft,  yield  easily  to  pressure,  swell 
up  to  double  their  bulk  when  soaked  in  weak  acids  or 
alkalies,  and  their  angles  have  not  the  constancy  peculiar 
to  ordinary  crystals.  Therefore  the  term  crystalloids,  i.e., 
having  the  likeness  of  crystals,  has  been  applied  to  them. 

As  Cohn  first  noticed  (Jour,  fur  Prakt.  Ckem.,  80,  p. 
129),  crystalloid  aleurone  may  be  observed  in  the  outer 
portions  of  the  potato  tuber,  in  which  it  invariably  pre- 
sents a  cubical  form.  It  is  best  found  by  examining  the 
cells  that  adhere  to  the  rind  of  a  potato  that  has  been 
boiled.  In  Fig.  21,  a  represents  a  cell  from  a  boiled 
potato,  in  the  center  of  which  is  seen  the  cube  of  aleurone. 
It  is  surrounded  by  the  exfoliated  remnants  of  starch- 
grains.  In  the  same  figure,  5  exhibits  the  contents  of  a 
cell  from  the  seed  of  the  bur  reed  (Sparganium  ramo- 
sum],  a  plant  that  is  common  along  the  borders  of  ponds. 
In  the  center  is  a  comparatively  large  mass  of  aleurone, 
having  crystalloid  facets. 

As  already  stated,  the  proteids  in  the  crystalloid  aleu- 
rones  of  hemp,  castor-bean  and  squash  have  the  chemical 
characters  of  globulin.  The  aleurone  of  the  Brazil-nut 
(Bertholletia)  and  that  of  the  yellow  lupin  contain,  ac- 
cording to  Hartig  and  Kubel,  9.4%  of  nitrogen  which 
corresponds  to  some  50  or  60%  of  proteids. 

Weyl  obtained  from  the  Brazil-nut  a  very  pure  amor- 
phous vitellin  with  18.1%  of  nitrogen.  The  vitellin  of 
Brazil-nut,  castor-bean,  and  of  hemp  and  squash  seeds  has 
been  recrystalized  from  salt  solutions  by  Schmiedeberg, 
Drechsel,  Griibler  and  Ritthausen.  According  to  Vines, 
seeds  of  lupin  and  peony  yield  a  myosin  to  salt-solution, 
and  sunflower  seeds,  after  treatment  with  ether  to  remove 
oil,  yield  a  globulin  with  the  properties  of  myosin,  but  if 
alcohol  is  used,  the  proteid  has  the  character  of  vitellin. 


THE  VOLATILE  PART  OF  PLANTS.       113 

Vines,  who  has  examined  the  aleurone  of  many  plants, 
finds  it  in  all  cases  more  or  less  soluble  in  water.  The 
globulin  doubtless  goes  into  solution  by  help  of  the  salts 
present.  Vines  also  states  that  a  body  soluble  in  water, 
having  the  properties  of  a  proteose  (hemialbumose),  is 
universally  present  in  aleurone. 

Estimation  of  the  Albuminoids. — The  quantitative  sep- 
aration of  these  bodies,  as  they  occur  in  plants,  is  mostly 
impossible  in  the  present  state  of  science.  In  many  cases 
their  collective  quantity  in  an  organic  substance  may  be 
calculated  with  approximate  accuracy  from  its  content  of 
nitrogen. 

In  calculating  the  nutritive  value  of  a  cattle-food  the 
albuminoids  are  currently  reckoned  as  equal  to  its  nitro- 
gen multiplied  by  6.25.  This  factor  is  the  quotient  ob- 
tained by  dividing  100  by  16,  which,  some  25  years  ago, 
when  cattle-feeding  science  began  to  assume  its  present 
form,  there  was  good  reason  to  assume  was  the  average 
per  cent  of  nitrogen  in  the  albuminoids.  As  Eitthausen 
has  insisted,  this  factor  is  too  small,  since  the  albuminoids 
of  the  cereals  and  of  most  leguminous  seeds,  as  well  as  of 
the  various  oil-cakes,  contain  nearer  17  than  16  per  cent 
of  nitrogen,  if  our  analyses  rightly  represent  their  com- 
position, and  the  factor  6  (=  100  -f-  16.66)  would  be 
more  nearly  correct. 

This  mode  of  calculation  only  applies  with  strictness 
where  all  the  nitrogen  exists  in  albuminoid  form.  This 
appears  to  be  substantially  true  in  most  seeds,  but  in  case 
of  young  grass  and  roots  there  is  usually  a  considerable 
proportion  of  non-albuminoid  nitrogen,  for  which  due 
allowance  must  be  made.  (See  Amides.)  * 

* Ammonia,  NH3,  and  Nitric  acid,  XHO3.  These  bodies  are  mineral,  not 
organic  substances,  and  are  not,  on  the  whole,  considerable  ingredients 
of  plants.  They  are  however  the  principal  sources  of  the  nitrogen  of 
vegetation,  and,  serving  as  plant-food,  enter  plants  through  their  roots, 
chiefly  from  the  soil,  and  exist  within  them  in  small  quantity,  and  for 
a  time,  pending  the  conversion  of  their  nitrogen  into  that  of  the 
amides  and  albuminoids,  to  whose  production  they  are  probably 
essential.  In  seeds  and  fruits,  and  in  mature  plants,  growing  in  soil* 


114:  HOW  CROPS  GEOW. 


AVERAGE  QUANTITY  OF  ALBUMINOIDS  IN  VARIOUS  VEGETABLE 
PBODUCTS.— ALBUMINOIDS  =  N  X  6.26. 

American,  Jenkins.  German,  Wolff, 

Maize  fodder,  green 1.8  1.9 

Beet  tops,             "     2.7  3.0 

Carrot  tops,         "      4.3  6.1 

Meadow  grass,  in  bloom 3.1  4.8 

Red  clover,                "        3.7  4.8 

White  clover,            "        4.0  6.6 

Turnips,  fresh 1.1  1.8 

Carrots,       "     1.1  2.2 

Potatoes,     "     2.2  3.4 

Corn  cobs,  air-dry 2.3  2.3 

Straw,                  "      3.5  4.0 

Pea  straw,          "      7.3  10.4 

Bean  straw,       "      10.2  16.3 

Meadow  hay ,  in  bloom 7.0  15.5 

Red-clover  hay,       "      12.5  19.7 

White-clover  hay,  "     14.6  23.2 

Buckwheat  kernel,  air-dry 10.0  14.4 


Barley 

Maize 

Rye 

Oat 

Wheat 

Pea 

Bean 


.12.4  16.0 

.10.6  16.0 

.10.6  17.6 

.11.4  17.6 

.11.8  20.8 

.22.4  35.8 

.24.1  40.8 


THE  AMIDES,  AMIDOACIDS,  IMIDES,  AND  AMINES. 
— Ammonia  and  the  ammonium  salts,  so  important  as 
food  to  plants,  and  as  ingredients  of  the  atmosphere,  of 
soils,  and  of  manures,  occur  in  so  small  proportions  in 
living  vegetation  as  to  scarcely  require  notice  in  this 
work  occupied  with  the  composition  of  Plants.  They 
are,  however,  important  in  connection  with  the  amides 
now  to  be  briefly  described.  Ammonia,  an  invisible  gas 
of  pungent  odor  which  dissolves  abundantly  in  water  to 
form  the  aqua  ammonia  of  spirits  of  hartshorn  of  the 
apothecary,  is  a  compound  of  one  atom  of  nitrogen  with 
three  atoms  of  hydrogen.  It  unites  to  acids,  forming 
the  ammonium  salts  : 


of  moderate  fertility,  both  ammonia  and  nitric  acid, .or  strictly  speak- 
ing, ammonia-salts  and  nitrates,  commonly  occur  in  very  small  pro- 
portions. In  roots,  stems,  and  foliage  of  plants  situated  in  soils  rich 
in  these  substances,  they  may  be  present  in  notable  quantity.  The 
dry  leaves  and  stems  of  tobacco  and  beets  sometimes  contain  several 
per  cent  of  nitrates.  When  these  substances  are  presented  to  plants  in 
abundance,  especially  in  dry  weather,  they  may  accumulate  in  the 
roots  and  lower  parts  of  the  plant  more  rapidly  than  they  can  be  assim- 
ilated. On  the  other  hand,  when  their  supply  in  the  soil  is  relatively 
small  they  are  so  completely  and  rapidly  assimilated  as  to  be  scarcely 
detectable.  Their  possible  presence  should  be  taken  into  account  when 
it  is  undertaken  to  calculate  the  albuminoids  of  the  plant  from  the 
amount  of  nitrogen  found  in  its  analysis. 


THE  VOLATILE  PART  OF  PLANTS.  115 


CHSCOOH  +  NHS  »  C 

Acetic  acid.  Ammonia.  Ammonium  acetate. 

Amides.  —  This  term  is  often  used  as  a  general  desig- 
nation for  all  the  bodies  of  this  section  which  result  from 
the  substitution  of  the  hydrogen  of  ammonia  by  any 
atom  or  group  of  atoms.  In  a  narrower  sense  amides 
are  those  ammonia-derivatives  containing  "acid-radi- 
cals "  which  are  indicated  in  their  systematic  names. 

Acetamide,  CHgCONH^  Many  ammonium  salts, 
when  somewhat  strongly  heated,  suffer  decomposition 
into  amides  and  water. 

CHSCOONH4          =  CHjCONH,          +  H,O 

Ammonium  acetate.  Acetamide.  Water. 

The  above  equation  shows  that  acetamide  is  ammonia, 
NH8,  or  HNH2,  one  of  whose  hydrogens  has  been  re- 
placed by  the  group  of  atoms,  CH3CO,  the  acetic  acid 
radical,  so  called.  Acetamide  is  a  white  crystalline  body. 
The  simple  amides,  like  acetamide,  are  as  yet  not  known 
to  exist  in  plants.  They  readily  unite  with  water  to 
produce  ammonium  salts. 

Carbamide,  or  Urea  CO(NH2)2.  This  substance  — 
the  amide  of  carbonic  acid  CO(OH)2  —  naturally  occurs 
in  considerable  proportion  in  the  urine  of  man  and  mam- 
malian animals.  It  is  a  white,  crystalline  body,  with  a 
cooling,  slightly  salty  taste,  which  readily  takes  up  the 
elements  of  water  and  passes  into  ammonium  carbonate. 
Urea  has  not  been  found  in  plants,  but  derivatives  of  it 
in  which  acid  radicals  replace  a  part  of  its  hydrogen  are 
of  common  occurrence.  (Guanin,  allantoin.) 

Amidoacids  are  acids  containing  the  NH2  group  as  a 
part  of  the  acid  radical. 

Amidoacetic  Acid,  C2H5N02,  or  CH2(NH2)COOH, 
is  derived  from  acetic  acid,  CH8COOH,  by  the  replace- 
ment of  H  in  CH8  by  NH2.  The  amidoacids  have  not  a 
sour,  but  usually  a  sweetish  taste,  and,  like  the  amides, 
act  both  as  weak  acids  and  weak  bases.  Amidoacetic 


116  HOW  CROPS  GROW. 

acid,  also  called  glycocoll,  has  not  as  yet  been  found  in 
plants,  but  exists  in  the  scallop  and  probably  in  other 
shell-fish,  and  a  compound  of  it,  benzoylglycocoll  or  hip- 
puric  acid,  is  a  nearly  constant  ingredient  of  the  urine  of 
the  horse  and  other  domestic  herbivorous  animals. 

Betain,  or  trimethylglycocoll,  C5HUN02,  a  crystalliza- 
ble  substance  found  in  beet-juice,  stands  in  close  chem- 
ical relations  to  amidoacetic  acid. 

Amidovaleric  acid,  CsHnNC^,  occurs  in  ox-pancreas 
and  in  young  lupin  plants.  Amidocaproic  acid,  or 
Leucin,  C6H13N02,  first  observed  in  animals,  has  lately 
been  discovered  in  various  plants.  The  same  is  true 
of  Tyrosin,  or  oxyphenyl-amidopropionic  acid, 
CsHnNOs,  and  of  phenyl  -  amidopropionic  acid, 
C9HUN02. 

The  above  amidoacids  are  readily  obtained  as  productf 
of  decomposition  of  animal  and  vegetable  albuminoids  by 
the  action  of  hot  acids.  Amidoacetic  acid  was  thus  first 
obtained  from  gelatin.  Leucin  and  Tyrosin  are  com- 
monly prepared  by  boiling  horn  shavings  with  dilute  sul- 
phuric acid ;  they  are  also  formed  from  vegetable  albu- 
minoids by  similar  treatment  and  are  final  results  of  the 
digestion  of  proto-  and  deutero-proteoses  (hemialbumose) 
under  the  action  of  trypsin  and  papain. 

Asparagin  and  Glutamin. — These  bodies,  which  are 
found  only  in  plants,  are  amides  of  amidoacids,  being  de- 
rived from  dibasic  acids.  Asparagin,  the  amide  of 
amidosuccinic  acid, 

CH(jSTH2)COOH 
CHjCOXH, 

has  been  found  in  very  many  plants,  especially  in  those 
just  sprouted,  as  in  asparagus,  peas,  beans,  etc.  Aspara- 
gin forms  white,  rhombic  crystals,  and  is  very  soluble  in 
water. 

Glutamin,  the  amide  of  amidoglutaric  acid, 


THE  VOLATILE  PART  OP  PLAKTS.  H7 

has  been  found,  together  with  asparagin,  in  beet-juice 
and  in  squash  seedlings.  , 

The  amides,  when  heated  with  water  alone,  and  more 
easily  in  presence  of  strong  acids  and  alkalies,  are  con- 
verted into  ammonia  and  the  acids  from  which  they  are 
derived.  Thus,  asparagin  yields  ammonia  and  amido- 
succinic  acid  at  the  boiling  heat  under  the  influence  of 
hydrochloric  acid,  or  of  potassium  hydroxide,  and  gluta- 
min  is  broken  up  by  the  last-named  reagent  at  common 
temperatures,  and  by  water  alone  at  the  boiling  point, 
with  formation  of  ammonia  and  amidoglutaric  acid. 

The  amidoacids  are  not  decomposed  by  hot  water  or 
acids  with  separation  of  ammonia.  Amidosuccinic  and 
amidoglutaric  acids  result  from  albuminoids  by  boiling 
with  dilute  sulphuric  acid,  and  by  the  action  of  bromine. 
The  latter  acid  as  yet  has  been  obtained  from  vegetable 
albuminoids  only,  and  is  prepared  most  abundantly  from 
gluten,  and  especially  from  mucedin. 

Imides,  closely  related  to  the  amides,  are  a  series  of 
very  interesting  substances,  into  whose  chemical  consti- 
tution we  cannot  enter  here  further  than  to  say  that  they 
contain  several  NH*  groups,  i.  e.,  ammonia,  NH8>  in 
which  two  hydrogens  are  replaced  by  hydro-carbon,  or 
oxycarbon  groups  or  carbon  atoms. 

These  bodies  are  Uric  acid,  C6H4N403,  Adenin,  C6H6N6, 
Guanin,  C5H5N50,  Allantoin,  C4H6N403,  Xanthin, 
Hypoxanthin,  C5H4lSr40,  Theobromin,  C7H80402,  Caffein, 
C,H10N402,  and  Vernin,  C16H20N808.  Of  these  the 
first,  so  far  as  now  known,  occurs  exclusively  in  the  ani- 
mal. Adenin,  Guanin,  Allantoin,  Xanthin,  and  Hypo- 
xanthin, are  common  to  animals  and  plants ;  the  last 
three  are  exclusively  vegetable. 

Caffein  exists  in  coffee  and  tea  combined  with  tannic 
acid.  In  the  pure  state  it  forms  white,  silky,  fibrous 
crystals,  and  has  a  bitter  taste.  In  coffee  it  is  found  to 

*  Or  its  hydro-carbon  derivatives. 


118  HOW  CROPS  GROW. 

the  extent  of  one-half  per  cent ;  in  tea  it  occurs  in  much 
larger  quantity,,  sometimes  as  high  as  6  per  cent. 

Theobromin  resembles  caffein  in  its  characters.  It 
is  found  in  the  cacao-bean,  from  which  chocolate  is  man- 
ufactured. 

Vernin,  discovered  recently  in  various  plants,  young 
clover,  vetches,  squash-seedlings,  etc.,  yields  guanin  by 
the  action  of  hydrochloric  acid.  All  these  bodies  stand 
in  close  chemical  relations  to  each  other,  being  complex 
imide  derivatives  of  dioxymalonic  (mesoxalic)  acid. 

The  amides  and  amidoacids,  like  ammonia,  are  able  to 
combine  directly  with  acids,  are  accordingly  bases,  but 
they  are  weak  bases,  because  the  basic  quality  of  their 
ammonia  is  largely  neutralized  by  the  acid  radicals  already 
present  in  them.  On  the  other  hand,  amides  and  ami- 
doacids often  act  as  weak  acids,  for  a  portion  of  the  hydro- 
gen of  the  jSTH2  group  is  easily  displaced  by  metals. 

The  amides  thus  in  fact  possess  in  a  degree  the  quali- 
ties of  both  the  acid  and  of  the  base  (ammonia)  from 
which  they  are  derived.  They  also  are  commonly  "neu- 
tral" in  the  sense  of  having  no  sharp  acid  or  alkaline 
taste  or  corrosive  character. 

In  vegetation  amides  appear  as  intermediate  stages  be- 
tween ammonium  salts  and  albuminoids.  They  are,  on 
the  one  hand,  formed  in  growing  plants  from  ammo- 
nium salts  by  a  constructive  process,  and  from  them  or 
by  their  aid,  probably,  the  albuminoids  are  built  up.  On 
the  other  hand,  in  animal  nutrition  they  are  stages 
through  which  the  elements  of  the  albuminoids  pass  in 
their  reversion  to  purely  mineral  matters.  In  germinat- 
ing seeds  and  developing  buds  they  probably  combine 
both  these  offices,  being  first  formed  in  the  germ  from, 
the  albuminoids  of  the  seed,  entering  the  young  plant  or 
shoot,  and  in  it  being  reconstructed  into  albuminoids. 
Their  free  solubility  in  water  and  ability  to  penetrate 
moist  membranes  adapt  them  for  this  movement.  They 


THE  VOLATILE  PART  OF  PLANTS.  119 

temporarily  accumulate  in  seedlings  and  buds,  but  disap- 
pear again  as  growth  takes  place,  being. converted  into 
albuminoids,  in  which  transformation  they  require  the 
conjunction  of  carbhydrates.  Their  ability  to  unite  with 
acid  as  well  as  bases  further  qualifies  them  to  take  part 
in  these  physiological  processes. 

The  imides  are  also  at  once  weak  bases  and  weak  acids. 
Uric  acid  and  allantoin,  relatively  rich  in  oxygen,  have 
the  acid  qualities  best  developed.  Guanin  and  caffein, 
with  less  oxygen  and  more  hydrogen,  are  commonly 
classed  among  the  organic  bases,  as  in  them  the  basic 
characters  are  most  evident. 

Amines. — When  the  hydrogen  of  ammonia  is  replaced 
by  hydrocarbon  groups  (radicals)  such  as  Methyl,  CH3, 
Ethyl,  C2H5,  Phenyl,  C6H5,  etc.,  compound  ammonias  or 
amines  result  which  often  resemble  ammonia  in  physical 
and  chemical  characters,  and  some  of  them  appear  to  be 
stronger  bases  than  ammonia,  being  able  to  displace  the 
latter  from  its  combinations. 

Trimethylamine,  N(CH3)8,  may  be  regarded  as  ammo- 
nia whose  hydrogens  are  all  substituted  by  the  methyl 
group,  CH3,  and  is  a  very  volatile  liquid  having  a  rank, 
fishy  odor,  which  may  be  obtained  from  herring  pickle,  and 
exhales  from  some  plants,  as  from  the  foliage  of  Chenopo- 
dium  vulvaria,  and  the  flowers  of  Crataegus  oxycantha. 
It  is  produced  from  detain  (trimethylamidoacetic  acid), 
by  heating  with  potash  solution,  just  as  ammonia  is 
formed  from  many  amides  under  similar  treatment. 

CJiolin,  C6H16N02,  and  Neurin,  C5H13NO,  are  organic 
bases  related  to  trimethylamine,  which  were  first  ob- 
tained from  the  animal.  Cholin  is  an  ingredient  of  the 
bile,  and  is  found  also  in  the  brain  and  yolk  of  eggs, 
where  it  exists  as  a  component  of  lecithin.  It  has  latterly 
been  discovered  in  the  hop,  lupin  and  pumpkin  plants, 
and  in  cotton  seed ;  by  oxidation  it  yields  betain.  Neu- 
rin is  readily  formed  from  cholin  by  the  action  of  alka- 


120  -HOW  CROPS  GEOW. 

lies  and  in  the  process  of  putrefaction.  It  is  a  violent 
poison,  and  is  perhaps  one  of  the  ingredients  which,  in 
the  seeds  of  the  vetch  and  of  cotton,  prove  injurious,  or 
even  fatal,  when  these  seeds  are  too  largely  eaten  by  ani- 
mals. Cholin  and  Neurin  are  syrupy,  highly  alkaline 
liquids. 

7.  ALKALOIDS  is  the  general  designation  that  has 
been  applied  to  the  organic  bases  found  in  many  plants, 
which  are  characterized  in  general  by  their  poisonous 
and  medicinal  qualities.  Caffein  and  Theobromin,  already 
noticed,  were  formerly  ranked  as  alkaloids.  We  may 
mention  the  following  : 

Nicotin,  Ci0H14N2,  is  the  narcotic  and  intensely  poi- 
sonous principle  in  tobacco,  where  it  exists  in  combina- 
tion with  malic  and  citric  acids.  In  the  pure  state  it  is 
a  colorless,  oily  liquid,  having  the  odor  of  tobacco  in  an 
extreme  degree.  It  is  inflammable  and  volatile,  and  so 
deadly  that  a  single  drop  will  kill  a  large  dog.  French 
tobacco  contains  7  or  8  per  cent;  Virginia,  6  or  7  per 
cent;  and  Maryland  and  Havana,  about  2  per  cent  of 
nicotin.  Nicotin  contains  17.3  per  cent  of  nitrogen, 
but  no  oxygen. 

Lupinidin,  C8Hi5lSr,  Lupanin,  CigH^^O,  and  Lu- 
pinin,  C2iH4oN202,  are  bases  existing  in  the  seeds  of  the 
lupin.  The  first  two  are  liquids  ;  the  last  is  a  crystal- 
line solid.  They  are  poisonous  and  are  believed  to  occa- 
sion the  sickness  which  usually  follows  the  use  of  lupin- 
seeds  in  cattle  food. 

Sinapin,  Ci6H28N06,  occurs  in  white  mustard.  When 
boiled  with  an  alkali  it  is  decomposed,  yielding  neurin 
as  one  product. 

Vicin,  C28H51Nn02i,  and  Convicin,  doH^NgO;,  are 
crystalline  bases  that  occur  in  the  seeds  of  the  vetch,  with 
regard  to  whose  nature  and  properties  little  is  known. 

Avenin,  C56H21NOi8,  according  to  Sanson,  is  a  sub- 
s.tance  of  alkaloidal  character,  existing  in  oats.  It  is  said 


THE  VOLATILE  PABT  OF  PLANTS.  121 

to  be  more  abundant  in  dark  than  in  light -colored  oats, 
and,  when  present  to  the  extent  of  more  than  nine-tenths 
of  one  per  cent,  to  act  as  a  decided  nerve-excitant  on  ani- 
mals fed  mainly  on  oats.  Avenin  is  described  as  a  gran- 
ular, brown,  non-crystallizable  substance,  but  neither 
Osborne  (at  the  Connecticut  Experiment  Station)  nor 
Wrampelmeyer  (Vs.  St.,  XXXVI,  p.  299)  have  been  able 
to  find  any  evidence  of  the  presence  of  such  a  body  in  oats. 

Morphin,  Ci7Hi9N03,  occurs,  together  with  several 
other  alkaloids,  in  opium,  the  dried  milky  juice  of  the 
seed-vessels  of  the  poppy  cultivated  in  India.  Its  use  in 
allaying  pain  and  obtaining  sleep  and  its  abuse  in  the 
"opium  habit"  are  well  known. 

Piperin,  Ci7H19N03,  the  active  principle  of  white  and 
black  pepper,  is  a  white  crystalline  body  isomeric  with 
morphin. 

Quinin,  C20H24!N"202,  is  the  most  important  of  several 
bases  used  as  anti-malarial  remedies  obtained  from  the 
bark  of  various  species  of  cinchona  growing  in  the  forests 
of  tropical  South  America,  and  cultivated  in  India. 

Strychnin,  C2iH22N202,  and  Brucin,  C28H26N20H,  ia 
the  intensely  poisonous  alkaloid  of  nux  vomica  (dog 
button). 

Atropin,  Ci7H23N08,  is  the  chief  poisonous  principle 
of  the  "  Nightshade"  or  belladonna,  and  of  stramonium 
or  "Jamestown  weed." 

Veratrin,  C32H49N09,  is  the  chief  toxic  ingredient  of 
the  common  White  Hellebore,  so  much  used  as  an 
insecticide. 

Solanin,  C42H87NOi6  (?),  is  a  poisonous  crystalline 
alkaloid  found  in  many  species  of  Solanum,  especially  in 
the  black  nightshade  (Solanum  nigrum).  It  occurs  in  the 
sprouted  tubers  and  green  fruit  of  the  potato  (Solanum 
tuberosum)  and  in  the  stems  and  leaves  of  the  tomato 
(Solanum  ly  coper  sicum). 

The  alkaloids,  so  far  as  investigated,  appear  to  be  more 


122  2*>W  CROPS  GBOW. 


or  less  complex  dsrivativss  of  the  bases  Pyridin,  C6H4N, 
and  Quinolin,  C9H7N,  which  are  colorless,  volatile 
liquids  with  sharp,  unpleasant  odor,  produced  from  albu- 
minoids at  high  temperatures,  and  existing  in  smoke, 
bone-oil  and  tar.  The  alkaloids  bear  to  these  bases  simi- 
lar relations  to  those  subsisting  between  the  amines  and 
ammonia. 

8.  PHOSPHOBIZED  SUBSTANCES.  —  This  class  of  bodies 
are  important  because  of  their  obvious  relations  to  the 
nutrition  of  the  brain  and  nerve  tissues  of  the  animal, 
which  have  long  been  known  to  contain  phosphorus  as 
an  essential  ingredient.  All  our  knowledge  goes  to  show 
that  phosphorus  invariably  exists  in  both  plants  and  ani- 
mals as  phosphoric  acid  or  some  derivative  of  this  acid, 
or,  in  other  words,  that  their  phosphorus  is  always 
united  to  oxygen  as  in  the  phosphates,  and  is  not  directly 
combined  to  carbon,  hydrogen,  or  nitrogen. 

Nuclein.  —  This  term  is  currently  employed  to  desig- 
nate various  imperfectly-studied  bodies  that  resemble  the 
albuminoids  in  many  respects,  but  contain  several  per 
cent  of  phosphorus.  They  are  easily  decomposable, 
boiling  water  being  able  to  remove  from  them  phosphoric 
acid,  and  under  the  action  of  dilute  acids  they  mostly 
yield  phosphoric  acid,  albuminoids  and  hypoxanthin, 
C5H4N40,  or  similar  imide  bases.  They  are  very  difficult 
of  digestion  by  the  gastric  juice.  The  nucleins  are  found 
in  the  protoplasm  and  especially  in  the  cell-nuclei  (see 
p.  245),  of  both  plants  and  animals,  and  have  been  ob- 
tained from  yeast,  eggs,  milk,  etc.,  by  a  process  based  on 
their  indigestibility  by  pepsin.  Chemists  are  far  from 
agreed  as  to  the  nature  or  composition  of  the  nucleins. 

Lecithin,  C^HgoNPOg.  —  This  name  applies  to  a  num- 
ber of  substances  that  have  been  obtained  from  the  brain 
and  nerve  tissue  of  animals,  eggs  and  milk,  as  well  as 
from  yeast,  and  the  seeds  of  maize,  peas,  and  wheat. 
The  lecithins  are  described  as  white,  wax-like  substances, 


THE  VOLATILE  PART  OF  PLANTS.  123 

imperfectly  crystallizable,  similar  to  protagon  in  their 
deportment  toward  water,  and  readily  decomposed  into 
cholin,  glycerophosphoric  acid,  and  one  or  more  fatty 
acids.  Three  lecithins  appear  to  have  been  identified, 
yielding  respectively,  on  decomposition,  stearic,  palmitic, 
and  oleic  acids. 

The  formula  C44H90NP09  is  that  of  distearic  lecithin, 
which  is  composed  of  glyceryl,  C3H5,  united  to  two 
stearic  acid  radicals,  and  also  to  phosphoric  acid,  which 
again  is  joined  to  cholin,  as  represented  by  the  formula— 


\OPO 

Lecithin  is  believed  to  be  a  constant  and  essential  in- 
gredient of  plants  and  animals. 

Protagon,  CieoHgosXePOss,  discovered  by  Liebreich  in 
the  brain  of  animals,  has  been  further  studied  by  Gam- 
gee  &  Blankenhorn.  It  is  a  white  substance  that  swells 
up  with  water  to  a  gelatinous  mass  and  finally  forms  an 
opake  solution.  From  solution  in  ether  or  alcohol  it  can 
be  easily  obtained  in  needle-shaped  crystals,  whose  com- 
position is  given  below.  Alkalies  decompose  protagon 
into  glycero-phosphoric  acid,  stearic  and  other  fatty 
acids,  and  cholin  or  neurin.  Protagon  was  formerly 
confounded  with  lecithin  and  thought  to  exist  in  plants, 
but  its  presence  in  the  latter  has  not  been  established. 

Protagon.  Lecithin. 

Carbon  .........................  66.39  65.43 

Hydrogen  ......................  10.69  11.16 

Nitrogen  ........................  2.39  1.73 

Phosphorus  ....................  1.07  3.84 

Oxygen  .........................  19.46  17.&i 

100.00  100.00 

Knop  was  the  first  to  show  that  the  crude  fat  which  is 
extracted  from  plants  by  ether  contains  an  admixture  of 
some  substance  of  which  phosphorus  is  an  ingredient. 
In  the  oil  obtained  from  the  sugar-pea  he  found  1.25  per 
cent,  of  phosphorus,  Topler  afterwards  examined  the 


124 


HOW  CROPS  GROW. 


oils  of  a  large  number  of  seeds  for  phosphorus  with  the 
subjoined  results  : 


Source  of  Per  cent,  of 

fat.  phosphorus. 

Lupin 0.29 

Pea 1.17 

Horse-bean 0.72 

Vetch 0.50 

Winter  lentil 0.39 

Horse-chestnut 0.40 

Chocolate-bean none 

Millet " 

Poppy " 


Source  of  Per  cent,  of 

fat.  phosphorus. 

Walnut trace 

Olive none 

Wheat 0.25 

Barley 0.28 

Rye 0.31 

Oat 0.44 

Flax none 

Colza " 

Mustard •* 


It  is  probable  that  the  phosphorus  in  these  oils  existed 
in  the  seeds  as  lecithin,  or  as  glycerophosphoric  acid, 
which  is  produced  in  the  decomposition  of  lecithin.  Max- 
well (Constitution  of  the  Legumes),  reckoning  from  the 
phosphoric  acid  found  in  the  ether-extract,  estimates  the 
pea  kernel  to  contain  0.368  per  cent,  the  horse-bean 
(Faba  vulgaris)  0.600  per  cent,  and  the  vetch  0.532  per 
cent  of  lecithin.  Lecithin  is  thus  calculated  to  make  up 
19.63  per  cent  of  the  crude  fat  of  the  pea,  31.54  per 
cent  of  the  crude  fat  of  the  horse-bean,  and  35.24  per 
cent  of  that  of  the  vetch. 

Chlorophyl,  i.  e.,  leaf -green,  is  the  name  applied  to 
the  substance  which  occasions  the  green  color  in  vegeta- 
tion. It  is  found  in  all  those  parts  of  most  annual  plants 
and  of  the  annually  renewed  parts  of  perennial  plants 
which  are  exposed  to  light.  The  green  parts  of  plants 
usually  contain  chlorophyl  only  near  their  surface,  and 
in  quantity  not  greater  than  one  or  two  per  cent  of  the 
fresh  vegetable  substance. 

Chlorophyl,  being  soluble  in  ether,  accompanies  fat  or 
wax  when  these  are  removed  from  green  vegetable  mat- 
ters by  this  solvent.  It  is  soluble  in  alcohol  and  hydro- 
chloric and  sulphuric  acids,  imparting  to  these  liquids  an 
intense  green  color,  but  it  suffers  alteration  and  decom- 
position so  readily  that  it  is  doubtful  if  the  composition 
of  chlorophyl,  as  it  exists  in  the  living  leaf,  is  accurately 
known,  especially  since  it  is  there  mixed  with  other  sub- 


THE  VOLATILE  PART  OF  PLANTS.  135 

stances,  separation  from  which  is  difficult  or  imprac- 
ticable. 

Chlorophyllan,  obtained  by  Hoppe-Seyler  from  grass, 
separates  from  its  solution  in  hot  alcohol  in  characteristic 
acicular  crystals  which  are  brown  to  transmitted  light, 
and  in  reflected  light  are  blackish  green,  with  a  velvety., 
somewhat  metallic  lustre.  This  substance  has  the  con- 
sistence of  beeswax,  adheres  firmly  to  glass,  and  at  about 
230°  melts  to  a  brilliant  black  liquid.  The  crystallized 
chlorophyllan  has  a  composition  as  follows  : 

CHLOROPHYLLAN. 

Carbon 73.36 

Hydrogen 9.72 

Nitrogen 5.68 

Phosphorus 1.38 

Magnesium 0.34 

Oxygen 9.52 

100.00 

Chlorophyllan  is  chemically  distinct  from  chlorophyl, 
as  proved  by  its  optical  properties,  but  in  what  the  dif- 
ference consists  is  not  understood.  Boiling  alkali  decom- 
poses it  with  formation  of  chlorophyllanic  acid  that 
may  be  obtained  in  blue-black  crystals,  and  at  the  same 
time  glycerophosphoric  acid  and  cholin,  the  decomposi- 
tion-products of  lecithin,  are  produced.  Tschirch  found 
that  chlorophyllan,  by  treatment  with  zinc  oxide,  yields 
a  substance  whose  optical  properties  lead  to  the  belief 
that  it  is  identical  with  the  chlorophyl  that  occurs  in  the 
living  plant.  It  was  obtained  as  a  dark-green  powder, 
but  its  exact  chemical  composition  is  not  known. 

The  special  interest  of  chlorophyl  lies  in  the  fact  that 
it  is  to  all  appearance  directly  concerned  in  those  con- 
structive processes  by  which  the  plant  composes  starch 
and  other  carbhydrates  out  of  the  mineral  substances 
which  form  its  food. 

Xanthophyl  is  the  yellow  coloring  matter  of  leaves 
and  of  many  flowers.  It  occurs,  together  with  chlorophyl, 
in  green  leaves,  and  after  disappearance  of  chlorophy] 
remains  as  the  principal  pigment  of  autumn  foliage. 


126  HOW  CROPS  GEOW. 


CHAPTER  IL 
THE  ASH  OF  PLANTS. 

II- 

THE  INGREDIENTS  OF  THE  A8H. 

As  has  been  stated,  the  volatile  or  destructible  part  of 
plants,  i.  e.,  the  part  which  is  converted  into  gases  or 
vapors  under  the  ordinary  conditions  of  burning,  con- 
sists chiefly  of  Carbon,  Hydrogen,  Oxygen  and  Nitro- 
gen, together  with  small  quantities  of  Sulphur  and  Phos- 
phorus. These  elements,  and  such  of  their  compounds 
as  are  of  general  occurrence  in  agricultural  plants,  viz., 
the  Organic  Proximate  Principles,  have  been  already 
described  in  detail. 

The  non-volatile  part  or  ash  of  plants  also  contains, 
or  may  contain,  Carbon,  Oxygen,  Sulphur,  and  Phos- 
phorus. It  is,  however,  in  general,  chiefly  made  up  of 
eight  other  elements,  whose  common  compounds  are 
permanent  at  the  ordinary  heat  of  burning. 

In  the  subjoined  table,  the  names  of  the  12  elements 
of  the  ash  of  plants  are  given,  and  they  are  grouped 
under  two  heads,  the  non-metals  and  the  metals,  by  rea- 
son of  an  important  distinction  in  their  chemical  nature. 

ELEMENTS  OF  THE  ASH  OF  PLANTS. 

Non-Metals.  Metals. 

Oxygen.  Potassium. 

Carbon.  Sodium. 

Sulphur.  Calcium. 

Phosphorus.  Magnesium. 

Silicon.  Iron. 

Chlorine.  Manganese. 

If  to  the  above  be  added 

Hydrogen  and  Nitrogen 


THE  ASH  OF  PLANTS.  127 

the  list  includes  all  the  elementary  substances  that  belong 
to  agricultural  vegetation. 

Hydrogen  is  never  an  ingredient  of  the  perfectly 
burned  and  dry  ash  of  any  plant. 

Nitrogen  may  remain  in  the  ash  under  certain  con- 
ditions in  the  form  of  a  Cyanide  (compound  of  Carbon 
and  Nitrogen),  as  will  be  noticed  hereafter. 

Besides  the  above,  certain  other  elements  are  found,  either  occasion- 
ally in  common  plants,  or  in  some  particular  kind  of  vegetation ;  these 
are  Iodine,  Bromine,  Fluorine,  Titanium,  Boron,  Arsenic,  Lithium, 
Rubidium,  Barium,  Aluminum,  Zinc,  Copper.  These  elements,  how- 
ever, so  far  as  known,  have  no  special  importance  in  agricultural 
chemistry,  and  mostly  require  no  further  notice. 

We  may  now  complete  our  study  of  the  Composition 
of  the  Plant  by  attending  to  a  description  of  those  ele- 
ments that  are  peculiar  to  the  ash,  and  of  those  com- 
pounds which  may  occur  in  it. 

It  will  be  convenient  also  to  describe  in  this  section 
some  substances,  which,  although  not  ingredients  of  the 
ash,  may  exist  in  the  plant,  or  are  otherwise  important 
to  be  considered. 

The  Non-metallic  Elements,  which  we  shall  first 
notice,  though  differing  more  or*less  widely  among  them- 
selves, have  one  point  of  resemblance,  viz.,  they  and  their 
compounds  with  each  other  have  acid  properties,  i.  e., 
they  either  are  acids  in  the  ordinary  sense  of  being  sour 
to  the  taste,  or  enact  the  part  of  acids  by  uniting  to  met- 
als or  metallic  oxides  to  form  salts.  We  may,  therefore, 
designate  them  as  the  acid  elements.  They  are  Oxygen, 
Sulphur,  Phosphorus,  Carbon,  Silicon,  and  Chlorine. 

With  the  exception  of  Silicon,  and  the  denser  forms  of 
Carbon,  these  elements  by  themselves  are  readily  volatile. 
Their  compounds  with  each  other,  which  may  occur  in 
vegetation,  are  also  volatile,  with  two  exceptions,  viz., 
Silicic  and  Phosphoric  acids. 

In  order  that  they  may  resist  the  high  temperature  at 
which  ashes  are  formed,  they  must  be  combined  with  the 
metallic  elements  or  their  oxides  as  salts. 


128  HOW  CEOPS  GEOW. 

Oxygen,  Symbol  0,  atomic  weight  16,  is  an  ingredient 
of  the  ash,  since  it  unites  with  nearly  all  the  other  ele- 
ments of  vegetation,  either  during  the  life  of  the  plant, 
or  in  the  act  of  combustion.  It  unites  with  Carbon, 
Sulphur,  Phosphorus,  and  Silicon,  forming  acid  bodies  ; 
while  with  the  metals  it  produces  oxides,  which  have  the 
characters  of  bases.  Chlorine  alone  of  the  elements  of 
the  plant  does  not  unite  with  oxygen,  either  in  the  living 
plant,  or  during  its  combustion. 

CAEBON  AND  ITS  COMPOUNDS. 

Carbon,  Sym.  C,  at.  wt.  12,  has  been  noticed  already 
with  sufficient  fullness  (p.  14).  It  is  often  contained  as 
charcoal  in  the  ashes  of  the  plant,  owing  to  its  being  en- 
veloped in  a  coating  of  fused  saline  matters,  which  shield 
it  from  the  action  of  oxygen. 

Carbon  Dioxide,  commonly  termed  Carbonic  acid, 
Sym.  C02,  molecular  zveight  44,  is  the  colorless  gas 
which  causes  the  sparkling  or  effervescence  of  beer  and 
soda  water,  and  the  frothing  of  yeast. 

It  is  formed  by  the  oxidation  of  carbon,  when  vegeta- 
ble matter  is  burned  (Exp.  6).  It  is,  therefore,  found 
in  the  ash  of  plants,  combined  with  those  bases  which  in 
the  living  organism  existed  in  union  with  organic  acids  ; 
the  latter  being  destroyed  by  burning. 

It  also  occurs  in  combination  with  calcium  in  the  tissues 
of  many  plants.  Its  compounds  with  bases  are  carbon- 
ates, to  be  noticed  presently.  When  a  carbonate,  as  mar- 
ble or  limestone,  is  drenched  with  a  strong  acid,  like 
vinegar  or  muriatic  acid,  the  carbon  dioxide  is  set  free 
with  effervescence. 

Carbonic  Acid,  H2C03,  or  CO(OH)2,  mo.  wt.  62. 
This,  the  carbonic  acid  of  modern  chemistry,  is  not  known 
as  a  distinct  substance,  since,  when  set  free  from  carbon- 
ates by  the  action  of  a  stronger  acid,  it  falls  ^nto  carbon 
dioxide  and  water : 


129 


CaCO3  +  2  HC1  =  CaCl,  +  H2CO3  and  H2CO3  =  H,O  -\-  COP 

Carbon  dioxide  is  also  termed  anhydrous  carbonic  acid, 
or  again,  carbonic  anhydride. 

CYANOGEN,  Sum,  C2>T2.— This  important  compound  of  Carbon  and  Ni- 
trogen is  a  gas  \vlncl»  has  an  odor  like  that  of  peach-pits,  and  \vhic> 
burns  011  contact  with  *  lighted  taper  with  a  fine  purple  flame.  In  its 
union  with  oxygen  by  combustion,  carbon  dioxide  is  formed,  and  nitro- 
gen set  free : 

CjN,  +  4  O  =  2  C02  +  N2. 

Cyanogen  may  be  prepared  bj"  heating  an  intimate  mixture  of  tw<? 
parts  by  weight  of  ferrocyanirie  if  potassium  (yellow  prussiate  of 
potash)  and  three  parts  of  corrosive  sublimate.  The  operation  may 
be  conducted  in  a  test-tube  or  small  flaslr,  to  the  mouth  of  which  is 
fitted  a  cork  penetrated  by  a  narrow  glas?  trbe.  On  applying  heat,  th6 
gas  issues,  and  may  be  set  on  fire  to  observe  its  beautiful  flame. 

Cyanogen,  combined  with  iron,  forms  the  Prussian  blue  of  com- 
merce, and  its  name,  signifying  the  blue-producer,  was  given  to  it  from 
that  circumstance. 

Cyanogen  unites  with  the  metallic  elements,  giving  rise  to  a  series 
of  bodies  which  are  termed  Cyanides.  Some  of  these  ofter?  occur  in 
small  quantity  in  the  ashes  of  plants,  being  produced  in  the  act  of 
burning  by  the  union  of  nitrogen  with  carbon  and  a  metal.  For  this 
result,  the  temperature  must  be  very  high,  carbon  must  be  in  excess, 
the  metal  is  usually  potassium  or  calcium,  the  nitrogen  may  be  either 
free  nitrogen  of  the  atmosphere  or  that  originally  existing  in  the 
organic  matter. 

With  hydrogen,  cyanogen  forms  the  deadly  poison  hydrocyanic  or 
prussic  acid,  HCy,  which  is  produced  from  amygdalin,  one  of  the  ingre- 
dients of  bitter  almonds,  peach,  and  cherry  seeds,  when  these  are 
crushed  in  contact  with  water. 

When  a  cyanide  is  brought  in  contact  with  steam  at  high  tempera- 
tures, it  is  decomposed,  all  its  nitrogen  being  converted  into  ammonia. 

Cyanogen  is  a  normal  ingredient  of  one  common  plant.  The  oil  of 
mustard  is  allylsulphocyanate,  C3H5CNS. 

SULPHUR  AND   ITS  COMPOUNDS. 

Sulphur,  Sym.  S,  at.  wt.  32. — The  properties  of  this 
element  have  been  already  described  (p.  25).  Some  of 
its  compounds  have  also  been  briefly  alluded  to,  but  re- 
quire more  detailed  notice. 

HYDROGEN  SULPHIDE,  Sym.  H,S,  mo.  u-t.  34.  This  substance,  familiarly 
known  as  sulphuretted  hydrogen,  occurs  dissolved  in  the  water  of  nu- 
merous so-called  sulphur  springs,  as  those  of  Avon  and  Sharon,  N.  Y., 
from  which  it  escapes  as  a  fetid  gas.  It  is  not  unfrequently  emitted 
from  volcanoes  and  fumaroles.  It  is  likewise  produced  in  the  decay  of 
organic  bodies  which  contain  sulphur,  especially  eggs,  the  intolerable 
odor  of  which,  when  rotten,  is  largely  due  to  this  gas.  It  is  evolved 
from  manur^.lieaps,  from  salt  marshes,  and  even  from  the  soil  of  moist 
meadows. 

9 


130  HOW  CROPS  GROW. 

The  ashes  of  plants  sometimes  yield  this  gas  when  they  are  moistened 
with  water.  In  such  cases,  a  sulphide  of  potassium  or  calcium  has  been 
formed  in  small  quantity  during  the  incineration. 

Hydrogen  Sulphide  is  set  free  in  the  gaseous  form  by  the  action  of  an 
acid  on  various  sulphides,  as  those  of  iron  (Exp.  17),  antimony,  etc.,  as 
well  as  by  the  action  of  water  on  the  sulphides  of  the  alkali  and  alkali- 
earth  metals.  It  may  be  also  generated  by  passing  hydrogen  gas  into 
melted  sulphur. 

Sulphuretted  hydrogen  has  a  slight  acid  taste.  It  is  highly  poisonous 
and  destructive,  both  to  animals  and  plants. 

SULPHUK  DIOXIDE,  commonly  called  SULPHUROUS  ACID,  Sym.  SO2,  mo. 
•wt.  &4.  When  sulphur  is  burned  in  the  air,  or  in  oxygen  gas,  it  forms 
copious  white  suffocating  fumes,  which  consist  of  one  atom  of  sulphur, 
united  to  two  atoms  of  oxygen ;  SO2  (Exp.  15). 

Sulphur  dioxide  is  characterized  by  its  power  of  discharging,  for  a 
time  at  least,  most  of  the  reel  and  blue  vegetable  colors.  It  has,  how- 
ever, no  action  on  many  yellow  colors.  Straw  and  wool  are  bleached 
by  it  in  the  arts. 

Sulphur  dioxide  is  emitted  from  volcanoes,  and  from  fissures  in  the 
soil  of  volcanic  regions.  It  is  produced  when  bodies  containing  sul- 
phur are  burned  with  imperfect  access  of  air,  and  is  thrown  into  the 
atmosphere  in  large  ^quantities  from  fires  which  are  fed  by  mineral 
coal,  as  well  as  from  the  numerous  roasting  heaps  of  certain  metallic 
ores  (sulphides)  which  are  wrought  in  mining  regions. 

Sulphur  dioxide  may  unite  with  bases,  yielding  salts  known  as  sul- 
phites, some  of  which,  viz.,  calcium  sulphite  and  sodium  sulphite,  are 
employed  to  check  or  prevent  fermentation,  an  effect  also  produced  by 
the  acid  itself. 

Sulphur-Trioxide,  Sym.  S03,  mo.  wt.  80,  is  known 
to  the  chemist  as  a  white,  silky  solid,  which  attracts 
moisture  with  great  avidity,  and,  when  thrown  into 
water,  hisses  like  a  hot  iron,  forming  sulphuric  acid. 
Sulphur  trioxide  was  formerly  termed  sulphuric  acid  or 
anhydrous  sulphuric  acid,  and  now  it  is  common  in 
statements  of  analysis  to  follow  this  usage. 

Sulphuric  Acid,  Sym.  H2S04,  mo.  wt.  98,  is  a  sub- 
stance of  the  highest  importance,  its  manufacture  being 
the  basis  of  the  chemical  arts.  In  its  concentrated  form 
it  is  known  as  oil  of  vitriol,  and  is  a  colorless,  heavy 
liquid,  of  an  oily  consistency,  and  sharp,  sour  taste. 

It  is  manufactured  on  the  large  scale  by  mingling  sul- 
phur dioxide  gas,  nitric  acid  gas,  and  steam,  in  large 
lead-lined  chambers,  the  floors  of  which  are  covered  with 
water.  The  sulphur  dioxide  takes  up  oxygen  from  the 


nitric  acid,  and  the  sulphuric  acid  thus  formed  dissolves 
in  the  water,  and  is  afterwards  boiled  down  to  the  proper 
strength  in  glass  vessels. 

The  chief  agricultural  application  of  sulphuric  acid  is 
in  the  preparation  of  "superphosphate  of  lime,"  which 
is  consumed  as  a  fertilizer  in  immense  quantities.  This 
is  made  by  mixing  together  sulphuric  acid,  somewhat 
diluted  with  water,  with  bone-dust,  bone-ash,  or  some 
mineral  phosphate.  Commercial  oil  of  vitriol  is  a  mix- 
ture of  sulphuric  acid  with  more  or  less  water.  The 
strongest  oil  of  vitriol  commonly  made,  or  "66°  acid," 
contains  93.5%  of  H2S04.  The  so-called  "60°  acid" 
contains  77.6%  H2S04  or  83%  of  66°  acid.  Chamber 
acid  or  "51°  acid"  contains  63.6%  H2S04,  or  67%  of 
66°  acid. 

Sulphuric  acid  occurs  in  the  free  state,  though  ex- 
tremely dilute,  in  certain  natural  waters,  as  in  the  Oak 
Orchard  Acid  Spring  of  Orleans,  N.  Y.,  where  it  is  pro- 
duced by  the  oxidation  of  sulphide  of  iron. 

Sulphuric  acid  is  very  corrosive  and  destructive  to  most 
vegetable  and  animal  matters. 

EXP.  53.— Stir  a  little  oil  of  vitriol  with  a  pine  stick.  The  wood  is  im- 
mediately browned  or  blackened,  and  a  portion  of  it  dissolves  in  the 
acid,  communicating  a  dark  color  to  the  latter.  The  commercial  acid 
is  often  brown  from  contact  with  straws  and  chips. 

Strong  sulphuric  acid  produces  great  heat  when  mixed  with  water, 
as  is  done  for  making  superphosphate. 

EXP.  54. — Place  in  a  thin  glass  vessel,  as  a  beaker  glass,  30  c.  c.  of  water ; 
into  this  pour  in  a  fine  stream  120  grams  of  oil  of  vitriol,  stirring  all  the 
while  with  a  narrow  test-tube,  containing  a  teaspoonful  of  water.  If  the 
acid  be  of  full  strength,  so  much  heat  is  thus  generated  as  to  boil  the 
water  in  the  stirring  tube. 

In  mixing  oil  of  vitriol  and  water,  the  acid  should  always  be  slowly 
poured  into  the  water,  with  stirring,  as  above  directed.  When  water 
is  added  to  the  acid,  it  floats  upon  the  latter,  or  mixes  with  it  but  super- 
ficially, and  the  liquids  may  be  thrown  about  by  the  sudden  formation 
of  steam  at  the  points  of  contact,  when  subsequently  stirred. 

Sulphuric  acid  forms  with  the  bases  an  important  class 
of  salts — the  sulphates,  to  be  presently  noticed — some  of 
which  exist  in  the  ash,  as  well  as  in  the  sap  of  plants. 


132  HOW  CEOPS  GROW. 

When  organic  matters  containing  sulphur — as  hair, 
albumin,  etc. — are  burned  with  full  access  of  air,  this 
element  remains  in  the  ash  as  sulphates,  or  is  partially 
dissipated  as  sulphur  dioxide. 

PHOSPHORUS  AND   ITS   COMPOUNDS. 

Phosphorus,  Sym.  P,  at.  wt.  31,  has  been  sufficiently 
described  (p.  27).  Of  its  numerous  compounds  but  two 
require  additional  notice. 

Phosphorus  Pentoxide,  Sym.  P206,  mo.  wt.  142, 
does  not  occur  as  such  in  nature.  When  phosphorus  is 
burned  in  dry  air  or  oxygen,  anbydrous  phosphoric  acid 
is  the  snow-like  product  (Exp.  18).  The  term  "phos- 
phoric acid,"  as  now  encountered  in  fertilizer  analyses, 
has  reference  to  "anhydrous  phosphoric  acid,"  as  phos- 
phorus pentoxide  was  formerly  designated.  Phosphorus 
pentoxide  has  no  sensible  acid  properties  until  it  has 
united  to  water,  which  it  combines  with  so  energetically 
as  to  produce  a  hissing  noise  from  the  heat  developed. 
On  boiling  it  with  water  for  some  time,  it  completely  dis- 
solves, and  the  solution  contains — 

Phosphoric  Acid,  Sym.  H3P04,  98.— The  chief  in- 
terest which  this  compound  has  for  the  agriculturist  lies 
in  the  fact  that  the  combinations  which  are  formed  be- 
tween it  and  various  bases— phosphates — are  among  the 
most  important  ingredients  of  plants  and  their  ashes. 

When  organic  bodies  containing  phosphorus,  as  le- 
cithin (p.  122),  and,  perhaps,  some  of  the  albuminoids, 
are  decomposed  by  heat  or  decay,  the  phosphorus  appears 
in  the  ashes  or  residue,  in  the  condition  of  phosphoric 
acid  or  phosphates. 

The  formation  of  several  phosphates  has  been  shown  in 
Exp.  20.  Further  account  of  them  will  be  given  under 
the  metals. 

CHLORINE   AND  ITS   COMPOUNDS. 

Chlorine,  Sym.  01.,  at.  wt.  35.5. — This  element  exists 


THE  ASH  OF  PLANTS.  133 

in  the  free  state  as  a  greenish-yellow,  suffocating  gas, 
which  has  a  peculiar  odor,  and  the  property  of  bleaching 
vegetable  colors.  It  is  endowed  with  the  most  vigorous 
affinities  for  many  other  elements,  and  hence  is  never  met 
with,  naturally,  in  the  free  state. 

EXP.  55. — Chlorine  may  be  prepared  by  heating  a  mixture  of  hydro- 
chloric acid  and  black  oxide  of  manganese  or  red-lead.  The  gas  being 
nearly  five  times  as  heavy  as  common  air,  may  be  collected  in  glass 
bottles  by  passing  the  tube  which  delivers  it  to  the  bottom  of  the  re- 
ceiving vessel.  Care  must  be  taken  not  to  inhale  it,  as  it  energetically 
attacks  the  interior  of  the  breathing  passages,  producing  the  disagree- 
able symptoms  of  a  cold. 

Chlorine  dissolves  in  water,  forming  a  yellow  solution. 

In  some  form  of  combination  chlorine  is  distributed 
over  the  whole  earth,  and  is  never  absent  from  the  plant. 

The  compounds  of  chlorine  are  termed  chlorides,  and 
may  be  prepared,  in  most  cases,  by  simply  putting  their 
elements  in  contact,  at  ordinary  or  slightly  elevated  tem- 
peratures. 

HYDROCHLORIC  ACID,  Sym.  HC1,  mo.  wt.  36.5.— When  Chlorine  and 
Hydrogen  gases  are  mingled  together,  they  slowly  combine  if  exposed 
to  diffused  light  ;  but  if  placed  in  the  sunshine,  they  unite  explosively, 
and  hydrogen  chloride  or  hydrochloric  acid  is  formed.  This  compound 
is  a  gas  that  dissolves  with  great  avidity  in  water,  forming  a  liquid 
which  has  a  sharp,  sour  taste,  and  possesses  all  the  characters  of  an 
acid. 

The  muriatic  aeid  of  the  apothecary  is  water  holding  in  solution 
several  hundred  times  its  bulk  of  hydrochloric  acid  gas,  and  is  pre- 
pared from  common  salt,  whence  its  ancient  name,  spirits  of  salt. 

Hydrochloric  acid  is  the  usual  source  of  chlorine  gas.  The  latter  is 
evolved  from  a  heated  mixture  of  this  acid  with  black  oxide  of  manga- 
nese. In  this  reaction  hydrogen  of  the  hydrochloric  acid  unites 
with  oxygen  of  the  oxide  of  manganese,  producing  water,  while 
chloride  of  manganese  and  free  chlorine  are  separated. 
4  HC1  +  MnOj  =  MnCl2  -f  2  Hs  O  +  2  Cl. 

When  chlorine,  dissolved  in  water,  is  exposed  to  the  sunlight,  there 
ensues  a  change  the  reverse  of  that  just  noticed.    Water  is  decom- 
posed, its  oxygen  is  set  free,  and  hydrochloric  acid  is  formed. 
HjO  +  2  Cl=  2  HC1  +  O. 

The  two  reactions  just  noticed  are  instructive  examples  of  the  differ- 
ent play  of  affinities  between  several  elements  under  unlike  circum- 
stances. 

This  acid  is  a  ready  means  of  converting  various  metals  or  metallic 
oxides  into  chlorides,  and  its  solution  in  water  is  a  valuable  solwnt 
and  reagent  for  the  purpose  of  the  chemist. 


134  HOW  CHOPS  GBOW. 

IODINE,  Sym.  I,  at.  ivt.  127.— This  interesting  body  is  a  black  solid  at 
ordinary  temperatures,  having  an  odor  resembling  that  of  chlorine. 
Sently  heated,  it  is  converted  into  a  violet  vapor.  It  occurs  in  sea- 
weeds, and  is  obtained  from  their  ashes.  It  gives  with  starch  a  blue  or 
purple  compound,  and  is  hence  employed  as  a  test  for  that  substance 
(p  49).  It  is  analogous  to  chlorine  in  its  chemical  relations.  It  is  not 
known  to  occur  in  sensible  quantity  in  agricultural  plants,  although  it 
may  well  exist  in  the  grasses  of  salt-bogs,  and  in  the  produce  of  soils 
which  are  manured  with  sea-weed. 

BROMINE  and  FLUORINE  may  also  exist  in  very  small  quantity  in 
plants,  but  these  elements  require  no  further  notice  in  this  treatise. 

SILICON  AND  ITS  COMPOUNDS. 

Silicon,  Sym.  Si,  at.  wt.  28. — This  element,  in  the 
free  state,  is  only  known  to  the  chemist.  It  may  be  pre- 
pared in  three  modifications  :  one,  a  brown,  powdery 
substance  ;  another,  resembling  plumbago,  and  a  third, 
that  occurs  in  crystals,  having  the  form  and  nearly  the 
hardness  of  the  diamond. 

Silicon  Dioxide,  Sym.  Si02,  mo.  wt.  60. — This  com- 
pound, known  also  as  Silica,  is  widely  diffused  in  nature, 
and  occurs  to  an  enormous  extent  in  rocks  and  soils,  both 
in  the  free  state  and  in  combination  with  other  bodies. 

Free  silica  exists  in  nearly  all  soils,  and  in  many  rocks, 
especially  in  sandstones  and  granites,  in  the  form  known 
to  mineralogists  as  quartz.  The  glassy,  white,  or  trans- 
parent, often  yellowish  or  red,  fragments  of  common  sand, 
which  are  hard  enough  to  scratch  glass,  are  almost  inva- 
riably this  mineral.  In  the  purest  state,  it  is  rock-crys- 
tal. Jasper,  flint,  and  agate  are  somewhat  less  pure 
silica. 

Silicates. — Silica  is  extremely  insoluble  in  pure  water 
and  in  most  acids.  It  has,  therefore,  none  of  the  sensi- 
ble qualities  of  acids,  but  is  nevertheless  capable  of  union 
with  bases.  It  is  slowly  dissolved  by  strong,  and  espe- 
cially by  hot,  solutions  of  potash  and  soda,  forming  sol- 
uble silicates  of  the  alkali  metals. 

EXP.  56.— Formation  of  potassium  silicate.  Heat  apiece  of  quartz  or 
flint,  as  large  as  a  chestnut,  as  hot  as  possible  in  the  fire,  and  quench 
suddenly  in  cold  water.  Reduce  it  to  fine  powder  in  a  porcelain  mor- 
tar, and  boil  it  in  a  porcelain  dish  with  twice  its  weight  of  caustic  pe*- 


THE  ASH  OF  PLANTS.  135 

ash,  and  eight  or  ten  times  as  much  water,  for  two  hours,  taking  care 
to  supply  the  water  as  it  evaporates.  Pour  off  the  whole  into  a  tall 
narrow  bottle,  and  leave  at  rest  until  the  undissolved  silica  has  settled. 
The  clear  liquid  is  a  basic  potassium  silicate,  i.  e.,  a  silicate  which  con. 
tains  a  number  of  molecules  of  base  for  each  molecule  of  silica.  It 
has,  in  fact,  the  taste  and  feel  of  potash  solution.  The  so-called  water' 
glass,  now  employed  in  the  arts,  is  a  similar  sodium  silicate. 

When  silica  is  strongly  heated  with  potash  or  soda,  or 
with  lime,  magnesia,  or  oxide  of  iron,  it  readily  melts  to- 
gether and  unites  with  these  bodies,  though  nearly  infus- 
ible by  itself,  and  silicates  are  the  result.  The  silicates 
thus  formed  with  potash  and  soda  are  soluble  in  water, 
like  the  product  of  Exp.  56,  when  the  alkali  exceeds  a 
certain  proportion — when  highly  basic  ;  but,  with  silica 
in  excess  (acid  silicates),  they  dissolve  with  difficulty. 
A  mixed  silicate  of  sodium,  calcium,  and  aluminum,  with 
a  large  proportion  of  silica,  is  nearly  or  altogether  insol- 
uble, not  only  in  water,  but  in  most  acids— constitutes, 
in  fact,  ordinary  glass. 

A  multitude  of  silicates  exist  in  nature  as  rocks  and 
minerals.  Ordinary  clay,  common  slate,  soapstone,  mica, 
or  mineral  isinglass,  feldspar,  hornblende,  garnet,  and 
other  compounds  of  frequent  and  abundant  occurrence, 
are  silicates.  The  natural  silicates  may  be  roughly  dis- 
tinguished as  belonging  to  two  classes,  viz.,  the  acid  sil- 
icates (containing  a  preponderance  of  silica)  and  basic 
silicates  (with  large  proportion  of  base).  The  former  are 
but  slowly  dissolved  or  decomposed  by  acids,  while  the 
latter  are  readily  attacked,  even  by  carbon  dioxide  acid. 
Many  native  silicates  are  anhydrous,  or  destitute  of 
water ;  others  are  hydrous,  i.  e.,  they  contain  water  as  a 
large  and  essential  ingredient. 

The  Silicic  Acids. — Various  silicic  acids — compounds 
of  silica  with  water — are  known  to  the  chemist,  or  are 
represented  by  the  silicates  found  in  nature.  The  silicic 
acids  themselves  have  little  stability  and  are  readily  re- 
solved into  water  and  silica. 

Soluble  Silicat  Si(OH)4?— This  body  is  known  only  in 


136  HOW  CEOPS  GROW. 

solution.  It  is  formed  when  the  solution  of  an  alkali- 
silicate  is  decomposed  by  means  of  a  large  excess  of  some 
strong  acid,  like  the  hydrochloric  or  sulphuric. 

EXP.  57.— Dilute  half  the  solution  of  potassium  silicate  obtained  in 
Exp.  56  with  ten  times  its  volume  of  water,  and  add  diluted  hydrochloric 
acid  gradually  until  the  liquid  tastes  sour.  In  this  Exp.  the  hydrochlo- 
ric acid  decomposes  and  destroys  the  potassium  silicate,  uniting  itself 
to  the  base  with  production  of  chloride  of  potassium,  which  dis- 
solves in  the  water  present.  The  silica  thus  liberated  unites  chemi- 
cally with,  water,  and  remains  also  in  solution. 

By  appropriate  methods  Doveri  and  Graham  have 
obtained  solutions  of  silica  in  pure  water.  Graham  pre- 
pared a  liquid  that  gave,  when  evaporated  and  heated, 
14  per  cent  of  anhydrous  silica.  This  solution  was  clear, 
colorless,  and  not  viscid.  It  reddened  litmus-paper  like 
an  acid.  Though  not  sour  to  the  taste,  it  produced  a 
peculiar  feeling  on  the  tongue.  Evaporated  to  dryness  at 
a  low  temperature,  it  left  a  transparent,  glassy  mass, 
which  had  the  composition  H2Si03.  This  dry  residue 
was  insoluble  in  water.  These  solutions  of  silica  in  pure 
water  are  incapable  of  existing  for  a  long  time  without 
suffering  a  remarkable  change.  Even  when  protected 
as  much  as  possible  from  all  external  agencies,  they 
sooner  or  later,  usually  in  a  few  days  or  weeks,  lose  their 
fluidity  and  transparency,  and  coagulate  to  a  stiff  jelly, 
from  the  separation  of  a  nearly  insoluble  hydrate  of  silica, 
which  we  shall  designate  as  gelatinous  silica. 

The  addition  of  7^^  of  an  alkali  or  earthy  carbon- 
ate, or  of  a  few  bubbles  of  carbon  dioxide  gas  to  the  strong 
solutions,  occasions  their  immediate  gelatinization.  A 
minute  quantity  of  potash  or  soda,  or  excess  of  hydro- 
chloric acid,  prevents  their  coagulation. 

Gelatinous  Silica. — This  substance,  which  results 
from  the  coagulation  of  the  soluble  silica  just  described, 
usually  appears  also  when  the  strong  solution  of  a  silicate 
has  strong  hydrochloric  acid  added  to  it,  or  when  a  sili- 
cate is  decomposed  by  direct  treatment  with  a  concen* 
trated  acid. 


THE  ASH  OF  PLANTS.  137 

It  is  a  white,  opaline,  or  transparent  jelly,  which,  on 
drying  in  the  air,  becomes  a  fine,  white  powder,  or  forms 
transparent  grains.  This  powder,  if  dried  at  ordinary 
temperatures,  has  a  composition  nearly  corresponding  to 
the  formula  H4Si308,  or  to  a  compound  of  3  Si02  with 
2  H20.  At  the  temperature  of  212°  F.,  it  loses  half  its 
water.  At  a  red  heat  it  becomes  anhydrous. 

Gelatinous  silica  is  distinctly,  though  very  slightly, 
soluble  in  water.  Fuchs  and  Bresser  have  found  by  ex- 
periment that  100,000  parts  of  water  dissolve  13  to  14 
parts  of  gelatinous  silica. 

The  hydrates  of  silica  which  have  been  subjected  to  a 
heat  of  212°,  or  more,  appear  to  be  totally  insoluble  in 
pure  water. 

These  hydrates  of  silica  are  readily  soluble  in  solutions 
of  the  alkalies  and  alkali  carbonates,  and  readily  unite 
with  moist,  slaked  lime,  forming  silicates. 

Exp.  58. — Gelatinous  Silica. — Pour  a  small  portion  of  the  solution  of 
silicate  potassium  of  Exp.  56  into  strong  hydrochloric  acid.  Gelatinous 
silica  separates  and  falls  to  the  bottom,  or  the  whole  liquid  becomes  a 
transparent  jelly. 

EXP.  59.— Conversion  of  soluble  into  insoluble  hydrated  silica. — Evapo- 
rate the  solution  of  silica  of  Exp.  57,  which  contains  free  hydrochloric 
acid,  in  a  porcelain  dish.  As  it  becomes  concentrated,  it  is  very  likely 
to  gelatinize,  as  happened  in  Exp.  58,  on  account  of  the  removal  of  the 
solvent.  Evaporate  to  perfect  dryiiess,  finally  on  a  water-bath  (i.  e.,  on 
a  vessel  of  boiling  water  which  is  covered  by  the  dish  containing  the 
solution).  Add  to  the  residue  water,  which  dissolves  away  the  chlo- 
ride of  potassium,  and  leaves  insoluble  hydrated  silioa,  3  SiO2  H2O,  a« 
a  gritty  powder. 

In  the  ash  of  plants,  silica  is  usually  found  in  com- 
bination with  alkali-metals  or  calcium,  owing  to  the 
high  temperature  to  which  it  has  been  subjected. 

In  the  plant,  however,  it  exists  chiefly,  if  not  entirely, 
in  the  free  state. 

TITANIUM,  an  element  which  has  many  analogies  with  silicon,  though 
rarely  occurring  in  large  quantities,  is  yet  often  present  in  the  form 
of  Titanic  acid,  TiO2,  in  rocks  and  soils,  and,  according  to  Salm-Hotst- 
mar,  may  exist  in  the  ashes  of  barley  and  oats. 

ARSENIC",  in  minute  quantity,  was  found  by  Davy  in  turnips  which 
had  been  manured  with  a  fertilizer  (superphosphate),  in  whose  pr»p- 
aration  arsenical  oil  of  vitriol  was  employed. 


138  HOW  CHOPS  GEOW. 

When  arsenic,  in  the  form  of  Paris  green  or  London  purple,  is  applied 
to  land  the  arsenic  soon  becomes  converted  into  highly  insoluble  iron 
compounds  and  is  not  taken  up  by  plants  in  appreciable  quantity. 

The  Metallic  Elements  which  remain  to  be  noticed, 
viz.:  Potassium,  Sodium,  Calcium,  Magnesium,  Iron, 
Manganese,  Aluminium,  Zinc,  and  Copper,  are  basic  in 
their  character,  i.  e.,  they  unite  with  the  acid  bodies 
that  have  just  been  described,  to  produce  salts.  Each 
one  is,  in  this  sense,  the  base  of  a  series  of  saline  com- 
pounds. 

ALKALI-METALS. — The  elements  Potassium  and  Sodium 
are  termed  alkali-metals.  Their  oxides  dissolve  in  and 
chemically  unite  to  water,  forming  hydroxides  that  are 
called  alkalies.  The  metals  themselves  do  not  occur  in 
nature,  and  can  only  be  prepared  by  tedious  chemical 
processes.  They  are  silvery-white  bodies,  and  are  lighter 
than  water.  Exposed  to  the  air,  they  quickly  tarnish 
from  the  absorption  of  oxygen  and  moisture,  and  are 
rapidly  converted  into  the  corresponding  alkalies. 
Thrown  upon  water,  they  mostly  inflame  and  burn  with 
great  violence,  decomposing  the  liquid.  Exp.  11. 

Of  the  alkali-metals,  Potassium  is  invariably  found  in 
all  plants.  Sodium  is  especially  abundant  in  marine  and 
strand  vegetation  ;  it  is  generally  found  in  agricultural 
plants,  but  is  sometimes  present  in  them  in  but  small 
quantity. 

POTASSIUM  AND    ITS    COMPOUNDS. 

Potassium,  Sym.  K  ;  *  at.  wt.  39. — "When  heated  in 
the  air,  this  metal  burns  with  a  beautiful  violet  light, 
and  forms  potassium  oxide. 

Potassium  Oxide,  or  Potash,  K20,  94,  is  the  so- 
called  ''actual  potash  "that  figures  in  the  analyses  of 
plants  and  valuation  of  fertilizers.  It  is,  however,  scarcely 
known  as  a  substance,  because  it  energetically  unites 
with  water  and  forms  hydroxide. 

*  From  the  Latin  name  Kalium. 


THE  ASH  OF  PLANTS.  139 

Potassium  Hydroxide,  KOH,  56,  is  tha  caustic 
potash  of  the  apothecary  and  chemist.  It  may  be  pro- 
cured in  white,  opaque  masses  or  sticks,  which  rapidly 
absorb  moisture  and  carbonic  acid  from  the  air,  and 
readily  dissolve  in  water,  forming  potash-lye.  It  strongly 
corrodes  many  vegetable  and  most  animal  matters,  and 
dissolves  fats,  forming  potash-soaps.  Both  the  oxide 
and  hydroxide  of  potassium  unite  to  acids  forming  salts. 

SODIUM  AND  ITS    COMPOUNDS. 

Sodium,  Na,*  23. — Burns  with  a  brilliant,  orange- 
yellow  flame,  yielding  sodium  oxide. 

Sodium  Oxide,  or  Soda,  Na20,  62,  is  practically  lit- 
tle known,  though  constantly  referred  to  as  the  base  of 
the  sodium  salts.  It  unites  to  water,  producing  the  hy- 
droxide. 

Sodium  Hydroxide,  or  Caustic  Soda,NaOH,  40. — 
This  body  is  like  caustic  potash  in  appearance  and  gen- 
eral characters.  It  forms  soaps  with  the  various  fats. 
While  the  potash-soaps  are  usually  soft,  those  made  with 
soda  are  commonly  hard. 

ALKALI-EARTH  METALS. — The  two  metallic  elements 
next  to  be  noticed,  viz.,  Calcium  and  Magnesium,  give, 
with  oxygen,  the  alkali-earths,  lime  and  magnesia.  The 
metals  are  only  procurable  by  difficult  chemical  pro- 
cesses, and  from  their  eminent  oxidability  are  not  found 
in  nature.  They  are  but  a  little  heavier  than  water. 
Their  oxides  are  but  slightly  soluble  in  water. 

CALCIUM  AND  ITS  COMPOUNDS. 

Calcium,  Ca,  40,  is  a  brilliant  ductile  metal  having  a 
light  yellow  color.  In  moist  air  it  rapidly  tarnishes  and 
acquires  a  coating  of  lime. 

Calcium  Oxide,  or  Lime,  CaO,   56,  is  the  result 

*  From  the  Latin  name  2f atrium. 


140  HOW  CROPS  GROW. 

of  the  oxidation  of  calcium.  It  is  prepared  for  nse 
in  the  arts  by  subjecting  limestone  or  oyster-shells  to  an 
intense  heat,  and  usually  retains  the  form  and  much  of 
the  hardness  of  the  material  from  which  it  is  made.  It 
has  the  bitter  taste  and  corroding  properties  of  the  alka- 
lies, though  in  a  less  degree.  It  is  often  called  quick 
lime,  to  distinguish  it  from  its  compound  with  water. 
It  may  occur  in  the  ashes  of  plants  when  they  have  been 
maintained  at  a  high  heat  after  the  volatile  matter  has 
been  burned  away. 

Calcium  Hydroxide,  Ca  (OH)2,  74.— Quick-lime, 
when  exposed  to  the  air,  gradually  absorbs  water  and 
falls  to  a  fine  powder.  It  is  then  said  to  be  air-slacked. 
When  water  is  poured  upon  quick-lime  it  penetrates  the 
oores  of  the  latter,  and  shortly  the  falling  to  powder  of 
the  lime  and  the  development  of  much  heat  give  evi- 
dence of  chemical  union  between  the  lime  and  the  water. 
This  chemical  combination  is  further  proved  by  the  in- 
crease of  weight  of  the  lime,  56  Ibs.  of  quick-lime  becom- 
ing 74  Ibs.  by  water-slacking.  On  heating  slacked  lime 
to  redness,  water  is  expelled,  and  calcium  oxide  remains. 

When  lime  is  agitated  for  some  time  with  much  water, 
tod  the  mixture  is  allowed  to  settle,  the  clear  liquid  is 
found  to  contain  a  small  amount  of  lime  in  solution  (one 
part  of  lime  to  700  parts  of  water).  This  liquid  is  called 
lime-water,  and  has  already  been  noticed  as  a  test  for 
carbonic  acid.  Lime-water  has  the  alkaline  taste  in  a 
marked  degree. 

MAGNESIUM  AND  ITS   COMPOUNDS. 

Magnesium,  Mg,  24. — Metallic  magnesium  has  a  sil- 
ver-white color.  When  heated  in  the  air  it  burns  with 
extreme  brilliancy  (magnesium  light),  and  is  converted 
into  magnesia. 

Magnesium  Oxide,  or  Magnesia,  MgO,  40,  is  found 
in  the  drug-stores  in  the  shape  of  a  bulky  white  powder, 


THE  ASH  OF  PLANTS.  141 

nncler  the  name  of  calcined  magnesia.  It  is  prepared  by 
subjecting  either  magnesium  hydroxide,  carbonate,  or 
nitrate,  to  a  strong  heat.  It  occurs  in  the  ashes  of 
plants. 

Magnesium  Hydroxide,  Mg(OH)2,  is  produced 
slowly  and  without  heat,  when  magnesia  is  mixed  with 
water.  It  occurs  rarely  as  a  transparent,  glassy  mineral 
(Brucite)  at  Texas,  Pa.,  Hoboken,  N.  J.,  and  a  few 
other  places.  It  readily  absorbs  carbon  dioxide  and  passes 
into  carbonate  of  magnesium.  Magnesium  hydroxide  is 
so  slightly  soluble  in  water  as  to  be  tasteless.  It  requires 
55,000  times  its  weight  of  water  for  solution  (Fresenius). 

HEAVY  METALS. — The  two  metals  remaining  to  notice 
are  Iron  and  Manganese.  These  again  considerably  re- 
semble each  other,  though  they  differ  exceedingly  from 
the  metals  of  the  alkalies  and  alkali-earths.  They  are 
about  eight  times  heavier  than  water.  Each  of  these 
metals  forms  two  basic  oxides,  which  are  commonly 
insoluble  in  pure  water. 

IRON  AND  ITS  COMPOUNDS. 

Iron,  Fe,*  56. — The  properties  of  metallic  iron  are  so 
well  known  that  we  need  not  occupy  any  space  in  reca- 
pitulating them. 

Ferrous  Oxide,  or  Protoxide  of  Iron,  FeO,  72. — 
When  sulphuric  acid  in  a  diluted  state  is  put  in  contact 
with  metallic  iron,  hydrogen  gas  shortly  begins  to  escape 
in  bubbles  from  the  liquid,  and  the  iron  dissolves,  unit- 
ing with  the  acid  to  form  ferrous  sulphate,  the  salt 
known  commonly  as  copperas  or  green-vitriol. 

'  H2SO4,  -f  Fe  =  FeSO4  +  Hr 

If,  now,  lime-water  or  potash-lye  be  added  to  the  solu- 
tion of  iron  thus  obtained,  a  white  or  greenish  white  pre- 
cipitate separates,  which  is  ferrous  hydroxide,  Fe(OH)9. 

•From  the  Latin  name  For  rum. 


HOW  CROPS  GROW. 

This  precipitate  rapidly  absorbs  oxygen  from  the  air,  be- 
coming black  and  finally  brown.  The  anhydrous  pro- 
toxide of  iron  is  black.  Carbonate  of  protoxide  of  iron 
is  of  frequent  occurrence  as  a  mineral  (spathic  iron),  and 
exists  dissolved  in  many  mineral  waters,  especially  in 
the  so-called  chalybeates.  The  ferrous  salts  are  mostly 
white  or  green. 

Ferric  Oxide,  or  Peroxide  of  Iron,  Fe208,  160. — 
When  ferrous  hydroxide  is  exposed  to  the  air,  it  acquires 
a  brown  color  from  union  with  more  oxygen,  and  becomes 
ferric  hydroxide  Fe(OH)3.  The  yellow  or  brown  rust 
which  forms  on  surfaces  of  metallic  iron  when  exposed  to 
moist  air  is  the  same  body.  Ferric  oxide  is  found  in 
the  ashes  of  all  agricultural  plants,  the  other  oxides  of 
iron  passing  into  this  when  exposed  to  air  at  high  tem- 
peratures. It  is  found  in  immense  beds  in  the  earth, 
and  is  an  important  ore  (specular  iron,  haematite).  It 
dissolves  in  acids,  forming  the  ferric  salts,  which  have 
a  yellow  color. 

MAGNETIC  OXIDE  OF  IRON,  Fe3O4,  or  FeO.Fe2O3,  is  a  combination 
of  the  two  oxides  above  mentioned.  It  is  black,  and  is  strongly  at- 
tracted by  the  magnet.  It  constitutes,  in  fact,  the  native  magnet,  or 
loadstone,  and  is  a  valuable,  ore  of  iron. 

MANGANESE  AND  ITS  COMPOUNDS. 

Manganese,  Mn,  55. — Metallic  manganese  is  difficult 
to  procure  in  the  free  state,  and  much  resembles  iron. 
Its  oxides  are  analogous  to  those  of  iron  just  noticed. 

Manganous  Oxide,  or  Protoxide  of  Manganese, 
MnO,  71,  has  an  olive-green  color.  It  is  the  base  of  all 
the  usually  occurring  salts  of  manganese.  Its  hydrox- 
ide, prepared  by  decomposing  manganous  sulphate  by 
lime-water,  is  a  white  substance,  which,  on  exposure  to 
the  air,  shortly  becomes  brown  and  finally  black  from 
absorption  of  oxygen.  The  manganous  salts  are  mostly 
pale  rose-red  in  color. 
MAXGAJJTC  OXIDE,  MnjO^  occurs  native  as  the  mineral  brauulte,  or, 


THE    ASH  OF  PLANTS.  143 

Combined  with  water,  as  manganite.  It  is  a  substance  having  a  red  or 
black-brown  color.  It  dissolves  in  cold  acids,  forming  salts  of  an  in- 
tensely red  color.  These  are,  however,  easily  decomposed  by  heat,  or 
by  organic  bodies,  into  oxygen  and  manganous  salts. 

RED  OXIDE  OF  MANGANESE,  MnsO4,  or  MnO .  MnaO8. — This  oxide  re- 
mains when  manganese  or  any  of  its  other  oxides  are  subjected  to  & 
high  temperature  with  access  of  air.  The  metal  and  the  protoxide 
gain  oxygen  by  this  treatment,  the  higher  oxides  lose  oxygen  until 
this  compound  oxide  is  formed,  which,  as  its  symbol  shows,  corres- 
ponds to  the  magnetic  oxide  of  iron.  It  is  found  in  the  ashes  of  plants. 

BLACK  OXIDE  OF  MANGANESE,  MnOa. — This  body  is  found  extensively 
in  nature.  It  is  employed  in  the  preparation  of  oxygen  and  chlorine 
(bleaching  powder),  and  is  an  article  of  commerce. 

Some  other  metals  occur  as  oxides  or  salts  in  ashes,  though  not  in 
such  quantity  or  in  such  plants  as  to  possess  any  agricultural  signifi- 
cance in  this  respect. 

ALUMINA,  AlaO3,  the  oxide  of  the  metal  Aluminium,  is  found  in 
considerable  quantity  (20  to  50  per  cent)  in  the  ashes  of  the  ground  pine 
(Lycopodlum).  It  is  united  with  an  organic  acid  (tartaric,  according  to 
Berzelius ;  malic,  according  to  Ritthausen)  in  the  plant  itself.  It  is 
often  found  in  small  quantity  in  the  ashes  6'f  agricultural  plants,  but 
whether  an  ingredient,  of  the  plant  or  due  to  particles  of  adhering  clay 
is  not  in  all  cases  clear. 

ZINO  has  been  found  in  a  variety  of  yellow  violet  that  grows  about 
the  zinc  mines  of  Aix-la-Chapelle. 

COPPER  is  frequently  present  in  minute  quantity  in  the  ash  of  plants, 
especially  of  such  as  grow  in  the  vicinity  of  manufacturing  establish- 
ments, where  dilute  solutions  containing  copper  are  thrown  to  waste. 

The  Salts  or  Compounds  of  Metals  with  Non- 
metals  found  in  the  ashes  of  plants  or  in  the  unburned 
plant  remain  to  be  considered. 

Of  the  elements,  acids  and  oxides,  that  have  been 
noticed  as  constituting  the  ash  of  plants,  it  must  be  re- 
marked that  with  the  exception  of  silica,  magnesia,  oxide 
of  iron,  ajid  oxide  of  manganese,  they  all  exist  in  the 
ash  in  the  form  of  salts  (compounds  of  acids  and  bases). 
In  the  living  agricultural  plant  it  is  probable  that,  of 
them  all,  only  silica  occurs  in  the  uncombined  state. 

We  shall  notice  in  the  first  place  the  salts  which  may 
occur  in  the  ash  of  plants,  and  shall  consider  them  under 
the  following  heads,  viz.  :  Carbonates,  Sulphates,  Phos- 
phates, and  Chlorides.  As  to  the  Silicates,  it  is  unnec- 
essary to  add  anything  here  to  what  has  been  already 
mentioned. 


144  HOW  CROPS  GEOW. 

THE  CARBONATES  which  occur  in  the  ashes  of  plants 
are  those  of  Potassium,  Sodium,  and  Calcium.  The 
Carbonates  of  Magnesium,  Iron,  and  Manganese  are  de- 
composed by  the  heat  at  which  ashes  are  prepared. 

Potassium  Carbonate,  or  Carbonate  of  Potash, 
K2C03,  114. — The  pearl-ash  of  commerce  is  a  tolerably 
pure  form  of  this  salt.  When  wood  is  burned,  the  potash 
which  it  contains  is  found  in  the  ash,  chiefly  as  carbon- 
ate. If  wood-ashes  are  repeatedly  washed  or  leached  with 
water,  all  the  salts  soluble  in  this  liquid  are  removed ;  by 
boiling  this  solution  down  to  dryness,  which  is  done  in 
large  iron  pots,  crude  potash  is  obtained,  as  a  dark  or 
brown  mass.  This,  when  somewhat  purified,  yields 
pearl-ash.  Potassium  carbonate,  when  pure,  is  white,  and 
has  a  bitter,  biting  taste — the  so-called  alkaline  taste.  It 
has  such  attraction  for  water,  that,  when  exposed  to  the 
air,  it  absorbs  moisture  and  becomes  a  liquid. 

If  hydrochloric  acid  be  poured  upon  this  carbonate  a 
brisk  effervescence  immediately  takes  place,  owing  to  the 
escape  of  carbon  dioxide  gas,  and  potassium  chloride  and 
water  are  formed,  which  remain  behind. 

KjCO3  +  2  HCl  =  2  KCl  +  H2O  +  COa. 

Potassium  Bicarbonate,  KHC08. — A  solution  ol 
potassium  carbonate,  when  exposed  to  carbon  dioxide,  ab- 
sorbs the  latter,  and  the  potassium  bicarbonate  is  pro- 
duced, so  called  because  to  a  given  amount  of.  potassium 
it  contains  twice  as  much  carbonic  acid  as  the  carbonate. 
Potash-salcBratus  consists  essentially  of  this  salt.  It 
probably  exists  in  the  juices  of  various  plants. 

Sodium  Carbonate,  or  Carbonate  of  Soda, 
Na2C08, 106. — This  substance,  so  important  in  the  arts, 
was  formerly  made  from  the  ashes  of  certain  marine 
plants  (Salsola  and  Salicornia),  in  a  manner  similar  to 
that  now  employed  in  wooded  countries  for  the  prepara- 
tion of  potash.  It  is  at  present  almost  wholly  obtained 


THE  ASH  OF  PLANTS.  145 

from  common  salt  by  somewhat  complicated  processes. 
It  occurs  in  commerce  in  an  impure  state  under  the  name 
of  Soda-ash.  United  to  water,  it  forms  sal-soda,  which 
usually  exists  in  transparent  crystals  or  crystallized 
masses.  These  contain  63  per  cent  of  water,  which 
partly  escapes  when  the  salt  is  exposed  to  the  air,  leav- 
ing a  white,  opaque  powder. 

Sodium  carbonate  has  a  nauseous  alkaline  taste,  not 
nearly  so  decided,  however,  as  that  of  the  carbonate  of 
potassium.  It  is  often  present  in  the  ashes  of  plants. 

Sodium  Bicarbonate,  NaHC03. — The  supercarbon- 
ate  of  soda  of  the  apothecary  is  this  salt  in  a  nearly  pure 
state.  The  cooking-soda  of  commerce  is  a  mixture  of 
this  with  some  simple  carbonate.  It  is  prepared  in  the 
same  way  as  potassium  bicarbonate.  The  bicarbonates, 
both  of  potassium  and  sodium,  give  off  half  their  carbonic 
acid  at  a  moderate  heat,  and  lose  all  of  this  ingredient 
by  contact  with  excess  of  any  acid.  Their  use  in  baking 
depends  upon  these  facts.  They  neutralize  any  acid 
(lactic  or  acetic)  that  is  formed  during  the  "  rising  "  of 
the  dough,  and  assist  to  make  the  bread  "  light "  by  in- 
flating it  with  carbon  dioxide. 

Calcium  Carbonate,  or  Carbonate  of  Lime, 
CaC03, 112. — This  compound  is  the  white  powder  formed 
by  the  contact  of  carbon  dioxide  with  lime-water.  When 
slacked  lime  is  exposed  to  the  air,  the  water  it  contains 
is  gradually  displaced  by  carbon  dioxide,  and  carbonate  of 
lime  is  the  result.  Air-slacked  lime  always  contains 
much  carbonate.  This  salt  is  distinguished  from  lime 
by  its  being  destitute  of  any  alkaline  taste. 

In  nature  carbonate  of  lime  exists  to  an  immense  ex- 
tent as  coral,  chalk,  marble,  and  limestone.  These 
rocks,  when  strongly  heated,  especially  in  a  current  of 
air,  part  with  carbon  dioxide,  and  quick-lime  remains 
behind. 

Calcium  carbonate  occurs  largely  in  the  ashes  of  most 
10 


146  HOW  CROPS  GROW. 

plants,  particularly  of  trees.  In  the  manufacture  ol 
potash  it  remains  undissolved,  and  constitutes  a  chief 
part  of  the  residual  leached  ashes. 

The  calcium  carbonate  found  in  the  ashes  of  plants  is 
supposed  to  come  mainly  from  the  decomposition  by  heat 
of  organic  calcium  salts  (oxalate,  tartrate,  malate,  etc. ), 
which  exist  in  the  juices  of  the  vegetable,  or  are  abun- 
dantly deposited  in  its  tissues  in  the  solid  form.  Car- 
bonate of  lime  itself  is,  however,  not  an  unusual  compo- 
nent of  vegetation,  being  found  in  the  form  of  minute, 
rhombic  crystals,  in  the  cells  of  a  multitude  of  plants. 

THE  SULPHATES  which  we  shall  notice  at  length  are 
those  of  Potassium,  Sodium,  and  Calcium.  Sulphate  of 
Magnesium  is  well  known  as  Epsom  salts,  and  Sulphate 
of  Iron  is  copperas  or  green  vitriol. 

Potassium  Sulphate,  or  Sulphate  of  Potash, 
K2S04,  174. — This  salt  may  be  procured  by  dissolving 
potash  or  carbonate  of  potash  in  diluted  sulphuric  acid. 
On  evaporating  its  solution,  it  is  obtained  in  the  form  of 
hard,  brilliant  crystals,  or  as  a  white  powder.  It  has  a 
bitter  taste.  Ordinary  potash,  or  pearl-ash,  contains 
several  per  cent  of  this  salt. 

Sodium  Sulphate,  or  Sulphate  of  Soda,  N"a2S04, 
142. — Glauber's  salt  is  the  common  name  of  this  famil- 
iar substance.  It  has  a  bitter  taste,  and  is  much  em- 
ployed as  a  purgative  for  cattle  and  horses.  It  exists, 
either  crystallized  and  transparent,  containing  10  mole- 
cules, or  nearly  56  per  cent  of  water,  or  anhydrous. 
The  crystals  rapidly  lose  their  water  when  exposed  to  the 
air,  and  yield  the  anhydrous  salt  as  a  white  powder. 

Calcium  Sulphate,  or  Sulphate  of  Lime,  CaS04, 
136. — The  burned  Plaster  of  Paris  of  commerce  is  this 
salt  in  a  more  or  less  pure  state.  It  is  readily  formed  by 
pouring  diluted  sulphuric  acid  on  lime  or  marble.  It  is 
found  in  the  ash  of  most  plants,  especially  in  that  of 
clover,  the  bean,  and  other  legumes. 


THE  ASH  OF  PLANTS.  14? 

In  nature,  sulphate  of  lime  is  usually  combined  with 
two  molecules  of  water,  and  thus  constitutes  Gypsum, 
CaS04 . 2  H20,  which  is  a  rock  of  frequent  and  exten- 
sive occurrence.  In  the  cells  of  many  plants,  as  for 
instance  the  bean,  gypsum  may  be  discovered  by  the 
microscope  in  the  shape  of  minute  crystals.  It  requires 
400  times  its  weight  of  water  to  dissolve  it,  and  being 
almost  universally  distributed  in  the  soil,  is  rarely  absent 
from  the  water  of  wells  and  springs. 

Land  plaster  is  ground  gypsum,  that  from  Nova 
Scotia  being  white,  that  from  Onondaga  and  other  local- 
ities in  New  York  State  gray  in  color. 

THE  PHOSPHATES  which  require  special  description 
are  those  of  Potassium,  Sodium,  and  Calcium. 

Numerous  phosphates  of  each  of  these  bases  exist,  or 
may  be  prepared  artificially.  But  three  classes  of  phos- 
phates have  any  immediate  interest  to  the  agriculturist. 
As  has  been  stated  (p  132),  phosphoric  acid,  prepared  by 
boiling  phosphorus  pentoxide  with  water,  is  represented 
by  the  symbol  H3P04.  The  phosphates  may  be  regarded 
as  phosphoric  acid  in  which  one,  two,  or  all  the  atoms 
of  hydrogen  are  substituted  by  one  or  several  metals. 

Potassium  Phosphates  or  Phosphates  of  Potash. 
—There  are  three  of  these  phosphates  formed  by  replac- 
ing one,  two,  or  three  hydrogen  atoms  of  phosphoric 
acid  by  potassium,  viz.  :  KH2P04,  primary  or  mono- 
potassic  phosphate ;  K2HP04,  secondary  or  dipotassic 
phosphate,  and  K8P04,  tertiary  or  tripotassic  phos- 
phate.* Of  these  salts,  the  secondary  and  tertiary  phos- 
phates exist  largely  (to  the  extent  of  40  to  50  per  cent) 
iu  the  ash  of  the  kernels  of  wheat,  rye,  maize,  and  other 
bread  grains.  The  potassium  phosphates  do  not  occur 
in  commerce ;  they  closely  resemble  the  corresponding 
sodium-salts  in  their  external  characters. 

*  The  primary  phosphates  are  often  designated  acid  or  auper-pJio» 
phates,  the  secondary  neutral  phosphates,  and  the  tertiary  basic  phoa 
phate*. 


148  HOW  CROPS  GBOW. 

Sodium  Phosphates,  or  Phosphates  of  Soda.— 
Of  these  the  disodic  phosphate,  Na2HP04,  alone  needs 
notice.  It  is  found  in  the  drug-stores  in  the  form  of 
glassy  crystals,  which  contain  12  molecules  (56  per  cent) 
of  water.  The  crystals  become  opaque  if  exposed  to  the 
air,  from  the  loss  of  water.  This  salt  has  a  cooling,  sa- 
line taste,  and  is  very  soluble  in  water. 

Calcium  Phosphates,  or  Phosphates  of  Lime. 
— Since  one  atom  of  calcium  replaces  two  of  hydrogen, 
the  formulae  of  the  calcium  phosphates  are  written  as 
follows  :  monocalcic  or  primary  phosphate  CaH4P208; 
dicalcic  or  secondary  phosphate,  CaHP04 ;  tricalcic  or 
tertiary  phosphate,  Ca3P208.*  Both  the  secondary  and 
tertiary  phosphates  probably  occur  in  plants.  The  sec- 
ondary is  a  white  crystalline  powder,  nearly  insoluble 
in  water,  but  easily  soluble  in  acids.  In  nature  it  is 
found  as  a  urinary  concretion  in  the  sturgeon  of  the  Cas- 
pian Sea.  It  is  also  an  ingredient  of  guanos,  and  proba- 
bly of  animal  excrements  in  general. 

The  tricalcic  phosphate,  or,  as  it  is  sometimes  termed, 
lone-phosphate,  is  a  chief  ingredient  of  the  bones  of  ani- 
mals, and  constitutes  90  to  95  per  cent  of  the  ash  or 
earth  of  bones.  It  may  be  formed  by  adding  a  solution 
of  lime  to  one  of  sodium  phosphate,  and  appears  as  a 
white  precipitate.  It  is  insoluble  in  pure  water,  but  dis- 
solves in  acids  and  in  solutions  of  many  salts.  In  the 
mineral  kingdom  tricalcic  phosphate  is  the  chief  ingre- 
dient of  apatite  and  phosphorite.  These  minerals  are 
employed  in  the  preparation  of  the  commercial  super- 
phosphates now  consumed  to  an  enormous  extent  as  a 
fertilizer.  Plain  superphosphate  is  essentially  a  mixture 
of  sulphate  of  lime  with  the  three  phosphates  above  no- 
ticed and  with  free  phosphoric  acid. 

The  Phosphates  of  Magnesium,  Iron,  Alumin- 
ium and  Manganese,  are  bodies  insoluble  in  water, 

*  These    formulae    correspond  to  2  molecules  of  phosphoric  acid* 

fcll6raO,j,  with  2  ami  4  li-utums  replaced  by  Cu. 


THE  ASH  OF  PLANTS.  149 

that  occur  in  very  small  proportion  in  the  ashes  of  plants 
and  in  soils,  but  are  important  ingredients  of  some 
fertilizers. 

THE  CHLORIDES  are  all  characterized  by  their  ready 
solubility  in  water.  The  Chlorides  of  Calcium  and  Mag- 
nesium are  deliquescent,  i.  e.,  they  liquefy  by  absorbing 
moisture  from  the  air.  The  Chlorides  of  Potassium  and 
Sodium  alone  need  to  be  described. 

Potassium  Chloride,  or  Muriate  of  Potash, 
KC1,  74.5. — This  body  may  be  produced  either  by  expos- 
ing metallic  potassium  to  chlorine  gas,  in  which  case  the 
two  elements  unite  together  directly ;  or  by  dissolving 
caustic  potash  in  hydrochloric  acid.  In  the  latter  case 
water  is  also  formed,  as  is  expressed  by  the  equation 
KHO  +  HC1  =  KC1  -j-  IPO. 

Potassium  chloride  closely  resembles  common  salt  in 
appearance,  solubility  in  water,  taste,  etc.  It  is  now  an 
important  article  of  commerce  and  largely  consumed  as 
a  fertilizer.  It  is  also  often  present  in  the  ash  and  in 
the  juices  of  plants,  especially  of  sea-weeds,  and  is  like- 
wise found  in  most  fertile  soils. 

Chloride  of  Sodium,  Nad,  58.5. — This  substance  is 
common  or  culinary  salt.  It  was  formerly  termed  muri- 
ate of  soda.  It  is  scarcely  necessary  to  speak  o*  its  oc- 
currence in  immense  quantities  in  the  water  of  the  ocean, 
in  saline  springs,  and  in  the  solid  form  as  rock-salt,  in 
the  earth.  Its  properties  are  so  familiar  as  to  require  no 
description.  It  is  rarely  absent  from  the  ash  of  plants. 

Besides  the  salts  and  compounds  just  described,  there 
occur  in  the  living  plant  other  substances,  most  of  which 
have  been  indeed  already  alluded  to,  but  may  be  noticed 
again  connectedly  in  this  place. 

These,  compounds,  being  destructible  by  heat,  do  not 
appear  in  the  analysis  of  the  ash  of  a  plant. 

NITRATES. — Nitric  acid  (the  compound  by  which  ni- 
trogen is  chiefly  furnished  to  plants  for  the  elaboration 


150  HOW  CROPS  GROW. 

of  the  albuminoid  principles)  is  not  unfrequently  pres- 
ent as  a  nitrate  in  the  tissues  of  the  plant.  It  usually 
occurs  there  as  potassium  nitrate  (niter,  saltpeter), 
KN03. 

The  properties  of  this  salt  scarcely  need  description. 
It  is  a  white,  crystalline  body,  readily  soluble  in  water, 
and  has  a  cooling,  saline  taste.  When  heated  with  car- 
bonaceous matters,  it  yields  oxygen  to  them,  and  a  defla- 
gration, or  rapid  and  explosive  combustion,  results. 
Touch-paper  is  paper  soaked  in  solution  of  niter  and 
dried.  The  leaves  of  the  sugar-beet,  sunflower,  tobacco, 
and  some  other  plants,  frequently  contain  this  salt,  and, 
when  burned,  the  nitric  acid  is  decomposed,  often  with 
slight  deflagration,  or  glowing  like  touch-paper,  and  the 
alkali  remains  in  the  ash  as  carbonate.  The  characters 
of  nitric  acid  and  the  nitrates  are  noticed  at  length  in 
"  How  Crops  Feed."  See  also  p 

OXALATES,  CITRATES,  MALATES,  TARTRATES,  and  salts 
of  other  less  common  organic  acids,  are  generally  to  be 
found  in  the  tissues  of  living  plants.  On  burning,  the 
metals  with  which  they  were  in  combination — potassium 
and  calcium,  in  most  cases — remain  as  carbonates. 

Ammonium  Salts  exist  in  minute  amount  in  some 
plants.  What  particular  salts  thus  occur  is  uncertain, 
and  special  notice  of  them  is  unnecessary  in  this  chapter. 

Since  it  is  possible  for  each  of  the  acids  above  described 
to  unite  with  each  of  the  bases  in  one  or  several  propor- 
tions, and  since  we  have  as  many  oxides  and  chlorides  as 
there  are  metals,  and  even  more,  the  question  at  once 
arises — which  of  the  60  or  more  compounds  that  may  thus 
be  formed  outside  the  plant  do  actually  exist  within  it  ? 
In  answer,  we  must  remark  that  while  most  or  all  of  them 
may  exist  in  the  plant  but  few  have  been  proved  to  exist 
as  such  in  the  vegetable  organism.  As  to  the  state  in 
which  iron  and  manganese  occur,  we  know  little  or  noth- 
ing, and  we  cannot  always  assert  positively  that  in  a  given 


THE  ASH  OF  PLANTS.  151 

plant  potassium  exists  as  phosphate,  or  sulphate,  or  car- 
bonate. We  judge,  indeed,  from  the  predominance  of 
potassium  and  phosphoric  acid  in  the  ash  of  wheat,  that 
potassium  phosphate  is  a  large  constituent  of  this  grain, 
but  of  this  we  are  scarcely  certain,  though  in  the  absence 
of  evidence  to  the  contrary  we  are  warranted  in  assuming 
these  two  ingredients  to  be  united.  On  the  other  hand, 
calcium  carbonate  and  calcium  sulphate  have  been  discov- 
ered by  the  microscope  in  the  cells  of  various  plants,  in 
crystals  whose  characters  are  unmistakable. 

For  most  purposes  it  is  unnecessary  to  know  more  than 
that  certain  elements  are  present,  without  paying  atten- 
tion to  their  mode  of  combination.  And  yet  there  is 
choice  in  the  manner  of  representing  the  composition  of 
a  plant  as  regards  its  ash-ingredients. 

We  do  not  indeed  so  commonly  speak  of  the  calcium 
or  the  silicon  in  the  plant  as  of  lime  and  silica,  because 
these  rarely-seen  elements  are  much  less  familiar  than 
their  oxides. 

Again,  we  do  not  speak  of  the  sulphates  or  chlorides, 
when  we  desire  to  make  statements  which  may  be  com- 
pared together,  because,  as  has  just  been  remarked,  we 
cannot  always,  nor  often,  say  what  sulphates  or  what 
chlorides  are  present. 

In  the  paragraphs  that  follow,  which  are  devoted  to  a 
more  particular  statement  of  the  mode  of  occurrence,  rel- 
ative abundance,  special  functions,  and  indispensability 
of  the  fixed  ingredients  of  plants,  will  be  indicated  the 
customary  methods  of  defining  them. 

§3. 

QUANTITY,  DISTRIBUTION,  AND  VARIATIONS  OF  THE  ASH- 
INGREDIENTS. 

The  Ash  of  plants  consists  of  the  various  acids,  oxides, 
and  salts,  that  have  been  noticed  in  §  1,  which  are  fixecl 
or  non- volatile  at  a  heat  near  redness. 


152  HOW  CEOPS  GROW. 

Ash-ingredients  axe  always  present  in  each  cell  of  every 
plant. 

The  ash-ingredients  exist  partly  in  the  cell-wall,  in- 
crusted  or  imbedded  in  the  cellulose,  and  partly  in  the 
plasma  or  contents  of  the  cell  (see  p  249). 

One  portion  of  the  ash-ingredients  is  soluble  in  water, 
and  occurs  in  the  juice  or  sap.  This  is  true,  in  general, 
of  the  salts  of  the  alkali-metals,  and  of  the  sulphates  and 
chlorides  of  magnesium  and  calcium.  Another  portion 
is  insoluble,  and  exists  in  the  tissues  of  the  plant  in  the 
solid  form.  Silica,  the  calcium  phosphates  and  the  mag- 
nesium compounds,  are  mostly  insoluble. 

The  ash-ingredients  may  be  separated  from  the  volatile 
matter  by  burning  or  by  any  process  of  oxidation.  In 
burning,  portions  of  sulphur,  chlorine,  alkalies,  and  phos- 
phorus may  be  lost,  under  certain  circumstances,  by  vola- 
tilization. The  ash  remains  as  a  skeleton  of  the  plant, 
and  often  actually  retains  and  exhibits  the  microscopic 
form  of  the  tissues. 

The  Proportion  of  Ash  is  not  Invariable,  even  ir 
the  same  kind  of  plant,  and  in  the  same  part  of  the  plant. 
Different  kinds  of  plants  often  manifest  very  marked  dif- 
ferences  in  the  quantity  of  ash  they  contain.  The  fol- 
lowing table  exhibits  the  amount  of  ash  in  100  parts  (of 
dry  matter)  of  a  number  of  plants  and  trees,  and  in  theii 
several  parts.  In  most  cases  is  given  an  average  proportion 
as  deduced  from  a  large  number  of  the  most  trustworthy 
examinations.  In  some  instances  are  cited  the  extreme 
proportions  hitherto  put  on  record. 

PROPORTIONS  OF  ASH  IN  VARIOUS  VEGETABLE  MATTERS.* 
ENTIRE  PLANTS,  BOOTS  EXCEPTED. 

Average.  Average. 


Red  clover 6.7 

White    "     7.2 

Timothy 7.1 

Potatoes  5.1 

Sugar  beet,  16.3—18.6 17.5 

Field  beet,  14.0—21.8 18.2 


Turnips/ 10.7— 19.7. 15.5 

Carrot,     15.0—21.3 17.1 

Hops 9.9 

Hemp 4.6 

Flax 4.3 

Heath 4.5 


THE  ASH  OP  PLANTS. 


ROOTS  AND  TUBERS. 


Potatoes,  2.6—8.0 4.1 

Sugar  beet,  2.9—6.0 4.4 

Field  beet,  2.8—11.3 7.7 


Turnip,  6.0— 20.9 12.0 

Carrot,  5.1—10.9 8.2 

Artichoke 5.2 


STRAW  AND  STEMS. 


Wheat,  3.8-€.9 5.4 

Rye,  4.9-^5.6 5.3 

Oats,  5.0—5.4 5.3 

Barley 6.8 


Peas,  6.5—9.4 „ 7.9 

Beans,  5.1— 7.2 6.1 

Flax 3.7 

Maize 5.5 


GRAINS  AND  SEED. 

Wheat,  1.5—3.1 2.0  '  Buckwheat,  1.1— 2.1 1.4 

Rye,  1.6—2.7 2.0    Peas,  2.4—2.9 2.7 

Oats,   2.5—1.0 3.3    Beans,  2.7— 4.3 3.7 

Barley,  1.8—2.8 2.3    Flax, 3.6 

Maize,  1.3—2.1 1.5  j  Sorghum 1.9 


WOOD. 


Beech 1.0 

Birch 0.3 

Grape 2.7 


Apple 1.3  |  Larch 


Red  Pine 0.3 

White  Pine 0.3 

Fir 0.3 

0.3 


Birch 1.3 

Red  Pine 2.8 

White  Pine 3.3 


Fir 2.0 

Walnut 6.4 

Cautotree 34.4 


From  the  above  table  we  gather  : — 

1.  That  different  plants  yield  different  quantities  of 
ash.     It  is  abundant  in  succulent  foliage,  like  that  of  the 
beet  (18  per  cent),  and  small  in  seeds,  wood,  and  bark. 

2.  That  different  parts  of  the  same  plant  yield  unlike 
proportions  of  ash.     Thus  the  wheat  kernel  contains  2 
per  cent,  while  the  straw  yields  5.4  per  cent.     The  ash 
in  sugar-beet  tops  is  17.5  ;  in  the  roots,  4.4  per  cent. 
In   the  ripe  oat,  Arendt  found  (Das  Wachsthum  der 
Haferpflanze,  p.  84), 

In  the  three  lower  joints  of  the  stem...  4.6  per  cent  of  ash. 
In  the  two  middle  joints  of  the  stem....  5.3 

In  the  one  upper  j  oint  of  the  stem 6.4 

In  the  three  lower  leaves 10.1 

In  the  two  upper  leaves 10.5 

In  the  ear 2.6 

3.  We  further  find  that,  in  general,  the  upper  and 
outer  parts  of  the  plant  contain  the  most  ash-ingredi- 
ents.    In  the  oat,  as  we  see  from  the  above  figures  of 
Arendt,  the  ash  increases  from  the  lower  portions  to  the 
upper,  until  we  reach  the  ear.     If,  however,  the  ear  be 


154  HOW  CEOPS  GEOW. 

dissected,  we  shall  find  that  its  outer  parts  are  richest  in 
ash.     Norton  found 

In  the  husked  kernels  of  brown  oats. ...  2.1  per  cent  of  ash. 

In  the  husk  of  brown  oats 8.2        "  " 

In  the  chaff  of  brown  oats 19.1        "  u 

Norton  also  found  that  the  top  of  the  oat-leaf  gave 
16.22  per  cent  of  ash,  while  the  bottom  yielded  but  13.66 
per  cent.  (Am.  Jour.  Science,  Vol.  Ill,  1847.) 

From  the  table  it  is  seen  that  wood  (0.3  to  2.7  per 
cent)  and  seeds  (1.5  to  3.7  per  cent) — lower  or  inner 
parts  of  the  plant — are  poorest  in  ash.  The  stems  of 
herbaceous  plants  (3.7  to  7.9  per  cent)  are  next  richer, 
while  the  leaves  of  herbaceous  plants,  which  have  such 
an  extent  of  surface,  are  the  richest  of  all  (6  to  8  per 
cent). 

4.  Investigation  has  demonstrated  further  that  the 
same  plant  in  different  stages  of  growth  varies  in  the  pro- 
portions of  ash  in  dry  matter,  yielded  both  by  the  entire 
plant  and  by  the  several  organs  or  parts. 

The  following  results,  obtained  by  Norton,  on  the  oat, 
illustrate  this  variation.  Norton  examined  the  various 
parts  of  the  oat-plant  at  intervals  of  one  week  through- 
out its  entire  period  of  growth.  He  found 

Leaves.  Stem.  Knots.     Chaff.  Grain  unhusked, 

June  4 10.8  10.4 

June  11 10.7  9.8 

June  18 9.0  9.3 

June  25 10.9  9.1 

July    2 11.3  7.8  4.9 

July   9 12.2  7.8  4.3 

July  16 12.6  7.9  6.0               3.3 

July  23 16.4  7.9  10.0             9.1                3.6 

July  30 16.4  7.4  9.6          12.2               4.2 

Aug.    6 16.0  7.6  10.4           13.7                4.3 

Aug.  13 20.4  6.6  10.4           18.6               4.0 

Aug.  20 21.1  6.6  11.7           21.0               3.6 

Aug.  27 22.1  7.7  11.2           22.4               3.5 

Sept.  3 20.9  8.3  10.7          27.4               3.6 

Here,  in  case  of  the  leaves  and  chaff,  we  observe  a  con- 
stant increase  of  ash,  while  in  the  stem  there  is  a  con- 


THE  ASH  OF  PLANTS.  155 

stant  decrease,  except  at  the  time  of  ripening,  when  these 
relations  are  reversed.  The  knots  of  the  stem  preserved 
a  pretty  uniform  ash-content.  The  unhusked  grain  at 
first  suffered  a  diminution,  then  an  increase,  and  lastly  a 
decrease  again. 

Arendt  found  in  the  oat-plant  fluctuations,  not  in  all 
respects  accordant  with  those  observed  by  Norton. 
Areudt  obtained  the  following  proportions  of  ash  : 


Slower 
joints  of 

2  middle 
joints  of 

Upper 
joint  of 

Lower 
leaves. 

Upper 
leaves. 

Ears. 

Entire 
plant. 

stem. 

stem. 

stem. 

June  18. 

..4.4 

9.7 

7.7 

8.0 

June  30. 

..2.5 

2.9 

as 

9.4 

7.0 

3.8 

62 

July  10. 

..3.5 

4.7 

52 

10.2 

6.9 

3.6 

5.4 

July  21. 

..4.4 

5.0 

5.5 

10.1 

9.7 

2.8 

52 

July  31. 

..6.4 

U 

6.4 

10.1 

10.5 

2.6 

5.1 

Here  we  see  that  the  ash  increased  in  the  stem  and  in 
each  of  its  several  parts  after  the  first  examination.  The 
lower  leaves  exhibited  an  increase  of  fixed  matters  after 
the  first  period,  while  in  the  upper  leaves  the  ash  dimin- 
ished toward  the  third  period,  and  thereafter  increased. 
In  the  ears,  and  in  the  entire  plant,  the  ash  decreased 
quite  regularly  as  the  plant  grew  older.  Pierre  found 
that  the  proportion  of  ash  of  the  colza  (Brassica  olera- 
cea)  diminished  in  all  parts  of  the  plant  (which  was 
examined  at  five  periods),  except  in  the  leaves,  in  which 
it  increased.  (Jdhresbericht  uber  Agriculturchemie,  III, 
p.  122.)  The  sugar-beet  (Bretschneider)  and  potato 
(Wolff)  exhibit  a  decrease  of  the  per  cent  of  ash,  both  in 
tops  and  roots. 

In  the  turnip,  examined  at  four  periods,  Anderson 
(Trans.  High,  and  Ag.  Soc. ,  1859-61,  p.  371)  found  the 
following  per  cent  of  ash  in  dry  matter  : 

July  7.      Aug.ll.      Sept.  I.       Oct.  5. 

Leaves 7.8  20.6  18£  16.2 

Bulbs 17.7  8.7  102  20.9 

In  this  case,  the  ash  of  the  leaves  increased  during 
about  half  the  period  of  growth  from  7.8  to  20.6,  and 


156  HOW  CROPS  GROW. 

thence  diminished  to  16.2.  The  ash  of  the  bulbs  fluc- 
tuated in  the  reverse  manner,  falling  from  17. 7  to  8. 7, 
then  rising  again  to  20.9. 

In  general,  the  proportion  of  ash  of  the  entire  plant 
diminishes  regularly  as  the  plant  grows  old. 

5.  The  influence  of  the  soil  and  season  in  causing  the 
proportion  of  ash  of  the  same  kind  of  plant  to  vary,  is 
shown  in  the  following  results,  obtained  by  Wunder 
Versuchs-Stationen,  IV,  p.  266)  on  turnip  bulbs,  raised 
during  two  successive  years,  in  different  soils. 

In  sandy  soil.  In  loamy  soil. 

1st  year.       2d  year.        1st  year.       2d  year. 
Percentofash 13.9  11.3  9.1  10.9 

6.  As  might  be  anticipated,  different  varieties  of  the 
same  plant,  grown  on  the  same  soil,  take  up  different 
quantities  of  non-volatile  matters. 

In  five  varieties  of  potatoes,  cultivated  in  the  same  soil 
and  under  the  same  conditions,  Herapath  (Qu.  Jour. 
Chem.,  Soc.  II,  p.  20)  found  the  percentages  of  ash  in 
dry  matter  of  the  tuber  as  follows  : 

VARIETY  OF  POTATO. 

White     Prince's      Axbridge  Forty- 
Apple.     Beauty.       Kidney.       Magpie,  fold. 
Ash  per  cent...  4.8              3.6               4.3                 3.4  3.9 

7.  It  has  been  observed  further  that  different  individ- 
uals of  the  same  variety  of  plant,  growing  side  by  side, 
on  the  same  soil  (in  the  same  field,  at  least),  contain  dif- 
ferent proportions  of  ash-ingredients,  according  as  they 
are,  on  the  one  hand,  healthy,  vigorous  plants,  or,  on  the 
other,  weak  and  stunted.     Pierre   (Jaliresbericht  uber 
Agriculturchemie,  III,    p.  125)   found  in  entire  colza 
plants  of  various  degrees  of  vigor  the  following  percent- 
ages of  ash  in  dry  matter  : 

In  extremely  feeble  plants,  1856 8.0  per  cent  of  ash: 

In  very  feeble  plants,  1857 9.0       "  " 

In  feeble  plants,  1857 11.4       "  «• 

In  strong  plants,  1857 11.0       «•  «• 

In  extre,jnely  strong  plants,  1857, . , , , , 14.3      "          •» 


THE  ASH  OF  PLANTS.  157 

Pierre  attributes  the  larger  per  cent  of  ash  in  the 
strong  plants  to  the  relatively  greater  quantity  of  leaves 
developed  on  them. 

Similar  results  were  obtained  by  Arendt  in  case  of  oats. 
Wunder  ( Versuchs-St.,  IV,  p.  115)  found  that  the  leaves 
of  small  turnip-plants  yielded  somewhat  more  ash  per 
cent  than  large  plants.  The  former  gave  19.7,  the  lat- 
ter 16.8  per  cent. 

8.  The  reader  is  prepared  from  several  of  the  foregoing 
statements  to  understand  partially  the  cause  of  the  vari- 
ations in  the  proportion  of  ash  in  different  specimens  of 
the  same  kind  of  plant. 

The  fact  that  different  parts  of  the  plant  are  unlike  in 
their  composition,  the  upper  and  outer  portions  being,  in 
general,  the  richer  in  ash-ingredients,  may  explain  in 
some  degree  why  different  observers  have  obtained  differ- 
ent analytical  results. 

It  is  well  known  that  very  many  circumstances  influ' 
ence  the  relative  development  of  the  organs  of  a  plant 
In  a  dry  season,  plants  remain  stunted,  are  rougher  on 
the  surface,  having  more  and  harsher  hairs  and  prickles, 
if  these  belong  to  them  at  all,  and  develop  fruit  earlier 
than  otherwise.  In  moist  weather,  and  under  the  influ- 
ence of  rich  manures,  plants  are  more  succulent,  and  the 
stems  and  foliage,  or  vegetative  parts,  grow  at  the  ex- 
pense of  the  reproductive  organs.  Again,  different  vari- 
eties of  the  same  plant,  which  are  often  quite  unlike  in 
their  style  of  development,  are  of  necessity  classed  to- 
gether in  our  table,  and  under  the  same  head  are  also 
brought  together  plants  gathered  at  different  stages  of 
growth. 

In  order  that  the  wheat  plant,  for  example,  should 
always  have  the  same  percentage  of  ash,  it  would  be  nec- 
essary that  it  should  always  attain  the  same  relative  de- 
velopment in  each  individual  part.  It  must,  then, 
always  grow  under  the  same  conditions  of  temperature, 


158  HOW  CROPS  GROW. 

light,  moisture,  and  soil.  This  is,  however,  as  good  as 
impossible,  and  if  we  admit  the  wheat  plant  to  vary  in 
form  within  certain  limits  without  losing  its  proper  char- 
acteristics, we  must  admit  corresponding  variations  in 
composition. 

The  difference  between  the  Tuscan  wheat,  which  is 
cultivated  exclusively  for  its  straw,  of  which  the  Leghorn 
hats  are  made,  and  the  "  pedigree  wheat "  of  Mr.  Hallett 
(Journal  Roy.  Ag.  Soc.  Eng.  Vol.  22,  p.  374),  is  in 
come  respects  as  great  as  between  two  entirely  different 
plants.  The  hat  wheat  has  a  short,  loose,  bearded  ear, 
containing  not  more  than  a  dozen  small  kernels,  while 
the  pedigree  wheat  has  shown  beardless  ears  of  8f  inches 
in  length,  closely  packed  with  large  kernels  to  the  num- 
ber of  120! 

Now,  the  hat  wheat,  if  cultivated  and  propagated  in 
the  same  careful  manner  as  has  been  done  with  the  pedi- 
gree wheat,  would,  no  doubt  in  time  become  as  prolific 
of  grain  as  the  latter,  while  the  pedigree  wheat  might 
perhaps  with  greater  ease  be  made  more  valuable  for  its 
straw  than  its  grain. 

We  easily  see  then,  that,  as  circumstances  are  perpet- 
ually making  new  varieties,  so  analysis  continually  finds 
diversities  of  composition. 

9.  Of  all  the  parts  of  plants,  the  seeds  are  the  least  lia- 
ble to  vary  in  composition.  Two  varieties  or  two  indi- 
viduals may  differ  enormously  in  their  relative  propor- 
tions of  foliage,  stem,  chaff,  and  seed ;  but  the  seeds 
themselves  nearly  agree.  Thus,  in  the  analysis  of  67 
specimens  of  the  wheat  kernel,  collated  by  the  author, 
the  extreme  percentages  of  ash  were  1.35  and  3.13.  In 
60  specimens  out  of  the  67,  the  range  of  variation  fell 
between  1.4  and  2.3  per  cent.  In  42  the  range  was  from 
1.7  to  2.1  per  cent,  while  the  average  of  the  whole  was 
2.1  per  cent. 

In  the  stems  or  straw  of  the  grains,  the  variation  is, 


THE  ASH  OF  PLANTS.  159 

much  more  considerable.  Wheat-straw  ranges  from  3.8 
to  6.9  ;  pea-straw,  from  6.5  to  9.4  per  cent.  In  fleshy 
roots,  the  variations  are  great ;  thus  turnips  range  from 
6  to  21  per  cent.  The  extremest  variations  in  ash-con- 
tent are,  however,  found,  in  general,  in  the  succulent 
foliage.  Turnip  tops  range  from  10.7  to  19.7;  potato 
tops  vary  from  11  to  near  20,  and  tobacco  from  19  to  27 
per  cent. 

Wolff  (Die  Naturgesetzlichen  Grundlagen  des  Acker- 
laus,  3  AufL,  p.  117)  has  deduced  from  a  large  number 
of  analyses  the  following  averages  for  three  important 
classes  of  agricultural  plants,  viz.  : 

Grain.  Straw. 

Cereal  crops.... 2  per  cent.        5.25  per  cent. 

Leguminous  crops 3    "       "  5        "       «« 

Oil-plants 4    "       "  4.5     "       «« 

More  general  averages  are  as  follows  (Wolff,  loe.  cit.)  : 


Annual  and  biennial  plants. 

Seeds 3  per  cent. 

Stems 5     "      " 

Roots 4     "      " 

Leaves 15    "      " 


Perennial  plants. 

Seeds 3  per  cent. 

Wood l      "     '« 

Bark 7     "      " 

Leaves 10     "     " 


We  may  conclude  this  section  by  stating  three  propo- 
sitions which  are  proved  in  part  by  the  facts  that  have 
been  already  presented,  and  which  are  a  summing  up  of 
the  most  important  points  in  our  knowledge  of  this  sub- 
ject. 

1.  Ash-ingredients  are  indispensable  to  the  life  and 
growth  of  all  plants.  In  mold,  yeast,  and  other  plants 
of  the  simplest  kind,  as  well  as  in  those  of  the  higher  or- 
ders, analysis  never  fails  to  recognize  a  proportion  of 
fixed  matters.  We  must  hence  conclude  that  these  are 
necessary  to  the  primary  acts  of  vegetation,  that  atmos- 
pheric food  cannot  be  assimilated,  that  vegetable  matter 
cannot  be  organized,  except  with  the  cooperation  of  those 
substances  which  are  invariably  found  in  the  ashes  of  the 
plant.  This  proposition  is  demonstrated  in  the  most 
conclusive  manner  by  numerous  synthetic  experiments* 


160  HOW  CROPS  GROW. 

It  is,  of  course,  impossible  to  attempt  producing  a  plant 
at  all  without  some  ash-ingredients,  for  the  latter  are 
present  in  all  seeds,  and  during  germination  are  trans- 
ferred to  the  seedling.  By  causing  seeds  to  sprout  in  a 
totally  insoluble  medium,  we  can  observe  what  happens 
when  the  limited  supply  of  fixed  matters  in  the  seeds  them- 
selves is  exhausted.  Wiegmann  &  Polstorf  (Preisschrift 
uber  die  unoryaniscfien  Bestandtheile  der  Pflanzen)  plant- 
ed 30  seeds  of  cress  in  fine  platinum  wire  contained  in  a 
platinum  vessel.  The  contents  of  the  vessel  were  moist- 
ened with  distilled  water,  and  the  whole  was  placed  under 
a  glass  shade,  which  served  to  shield  from  dust.  Through 
an  aperture  in  the  shade,  connection  was  made  with  a  gas- 
ometer, by  which  the  atmosphere  in  the  interior  could  be 
renewed  with  an  artificial  mixture,  consisting,  in  100,  of 
21  parts  oxygen,  78  parts  nitrogen,  and  1  part  carbonic 
acid.  In  two  days  28  of  the  seeds  germinated  ;  afterwards 
they  developed  leaves,  and  grew  slowly  with  a  healthy  ap- 
pearance during  26  days,  reaching  a  height  of  two  or 
three  inches.  From  this  time  on,  they  refused  to  grow, 
began  to  turn  yellow,  and  died  down.  The  plants  were 
collected  and  burned  ;  the  ash  from  them  weighed  pre- 
cisely as  much  as  that  obtained  by  burning  28  seeds  like 
those  originally  sown.  This  experiment  demonstrates 
most  conclusively  that  a  plant  cannot  grow  in  the  absence 
of  those  substances  found  in  its  ash.  The  development 
of  the  cresses  ceased  so  soon  as  the  fixed  matters  of  the 
seed  had  served  their  utmost  in  assisting  the  organization 
of  new  cells.  We  know  from  other  experiments  that,  had 
the  ashes  of  cress  been  applied  to  the  plants  in  the  above 
experiment,  just  as  they  exhibited  signs  of  unhealthiness, 
they  would  have  recovered,  and  developed  to  a  much  great- 
er extent. 

II.  The  proportion  of  ash-ingredients  in  the  plant  is 
variable  within  a  narrow  range,  but  cannot  fall  below  or 
exceed  certain  limits.  The  evidence  of  this  proposition 


THE  ASH  OF  PLANTS.  161 

is  to  be  gathered  both  from  the  table  of  ash-percentages 
and  from  experiments  like  that  of  Wiegmann  &  Polstorf, 
«bove  described. 

III.  We  have  reason  to  believe  that  each  part  or  organ 
(each  cell)  of  the  plant  contains  a  certain,  nearly  invaria- 
ble, amount  of  fixed  matters, which  is  indispensable  to  the 
vegetative  functions.  Each  part  or  organ  may  contain, 
besides,  a  variable  and  unessential  or  accidental  quantity 
of  the  same.  What  portion  of  the  ash  of  any  plant  is  es- 
sential and  what  accidental  is  a  question  not  yet  brought 
to  a  satisfactory  decision.  By  assuming  the  truth  of  this 
proposition,  we  account  for  those  variations  in  the 
amount  of  ash  which  cannot  be  attributed  to  the  causes 
already  noticed.  The  evidences  of  this  statement  must 
be  reserved  for  the  subsequent  section. 

§Q 
o. 

SPECIAL    COMPOSITION  OF  THE  ASH    OF   AGEICT7LTUEAL 
PLANTS. 

The  result  of  the  extended  inquiries  which  have  been 
made  into  the  subject  of  this  section  may  be  convenient- 
ly presented  and  discussed  under  a  series  of  propositions, 
viz.: 

1.  Among  the  substances  which  have  been  described 
(§  I)   as  the  ingredients  of  the  ash,  the  following  are  in- 
variably present  in  all  agricultural  plants,  and  in  nearly 
all  parts  of  them,  viz. : 

f Potash,  K,O.  (Chlorine,  Cl. 

Soda,  Na,O.  Sulphuric  acid,  SO,. 

Bases  1  Lime,  Cat).  Acids  <  Phosphoric  acid,  P.OS. 

Magnesia,  MgO.  Silicic  acid,  SiO.. 

(.Oxide  of  iron,  Fe2O3.  ^Carbonic  acid,  CO2. 

2.  Different  normal  specimens  of    the  same  kind   of 
plant  have  a  nearly  constant  composition.     The  use  of 
the  word  nearly  in  the  above  statement  implies  what  has 
been  already  intimated,  viz.,  that  some  variation  is  noticed 
in  the  relative  proportions  as  well  as  in  the  total  quantity 

11 


162  HOW  CROPS  GBOW. 

of  ash-ingredients  occurring  in  plants.  This  point  will 
shortly  be  discussed  in  full.  By  taking  the  average  of 
many  trustworthy  ash-analyses  we  arrive  at  a  result  which 
does  not  differ  very  widely  from  the  majority  of  the  in- 
dividual analyses.  This  is  especially  true  of  the  seeds  of 
plants,  which  attain  nearly  the  same  development  under 
all  ordinary  circumstances.  It  is  less  true  of  foliage  and 
roots,  whose  dimensions  and  character  vary  to  a  great 
extent.  In  the  following  tables  (p.  164-170)  is  stated  the 
composition  of  the  ashes  of  a  number  of  agricultural 
products  which  have  been  repeatedly  subjected  to  analy- 
sis. In  most  cases,  instead  of  quoting  all  the  individual 
analyses,  a  series  of  averages  is  given.  Of  these,  the  first 
is  the  mean  of  all  the  analyses  on  record  or  obtainable  by 
the  writer,*  while  the  subsequent  ones  represent  either 
the  results  obtained  in  the  examination  of  a  number  of 
samples  by  one  analyst,  or  are  the  means  of  several  single 
analyses.  In  this  way,  it  is  believed,  the  real  variations 
of  composition  are  pretty  truly  exhibited,  independently 
of  the  errors  of  analysis. 

The  lowest  and  highest  percentages  are  likewise  given. 
These  are  doubtless  in  many  cases  exaggerated  by  errors  of 
analysis,  or  by  impurity  of  the  material  analyzed.  Chlo- 
rine and  sulphuric  acid  are  for  the  most  part  too  low,  be- 
cause they  are  liable  to  be  dissipated  in  combustion,  while 
silica  is  often  too  high,  from  the  fact  of  sand  and  soil  ad- 
hering to  the  plant. 

In  two  cases,  single  and  doubtless  incorrect  analyses  by 
Bichon,  which  give  exceptionally  large  quantities  of  soda, 
are  cited  separately. 

A  number  of  analyses  that  came  to  notice  after  making 
out  the  averages  are  given  as  additional. 

*  At  the  time  of  preparing  the  first  edition  of  this  book,  in  1868.  More 
recent  analyses  are  comparatively  few  in  number,  excepting  those  of 
wheat  (grain  and  straw)  by  Lawes  &  Gilbert,  and  do  not  diner  essen- 
tially from  those  given.  The  numerous  very  incorrect  ash-analyses, 
published  by  Dr.  E.  Emmons  and  Dr.  J.  H.  Salisbury,  in  the  Natural 
History  of  New  York,  and  in  the  Trans,  of  the  New  York  State  Agricul' 
tural  Society,  are  not  included. 


THE  ASH  OP  PLANTS.  163 

The  following  table  includes  both  the  kernel  and  straw 
of  Wheat,  Rye,  Barley,  Oats,  Maize,  Rice,  Buckwheat, 
Beans,  and  Peas  ;  the  tubers  of  Potatoes  ;  the  roots  and 
tops  of  Sugar-Beets,  Field-Beets,  Carrots,  Turnips,  and 
various  parts  of  the  Cotton  Plant. 

For  the  average  composition  of  other  plants  and  vege- 
table products,  the  reader  is  referred  to  a  table  in  the  ap- 
pendix, p.  409,  compiled  by  Prof.  Wolff,  of  the  Royal 
Agricultural  Academy  of  Wiirtemberg.  That  table  in- 
cludes also  the  averages  obtained  by  Prof.  Wolff  for  most 
of  the  substances,  cotton  excepted,  whose  composition  is 
represented  in  the  pages  immediately  following. 

In  both  tables  the  carbonic  acid,  CO2,  which  occurs  in 
most  ashes,  is  excluded,  from  the  fact  that  its  quantity 
varies  according  to  the  temperature  at  which  the  ash  is 
prepared. 

The  following  is  a  statement  of  the  various  Names  and 
Symbols  that  are  or  have  been  currently  applied  to  the 
Ash-Ingredients  in  Chemical  Literature.  The  changes 
that  have  been  made  from  time  to  time,  both  in  symbols 
and  in  names,  are  the  results  of  progress  in  knowledge  or 
of  attempts  to  improve  nomenclature  : 

Older  Newer 

Symbols.       Symbol*.  Synonyms. 

KO  KjO         Potash,  Potassa,  Potassium  Oxide,  Potassic  Oxide. 

NaO  Na,O       Soda,  Sodium  Oxide,  Sodic  Oxide. 

MgO  MgO        Magnesia,  Magnesium  Oxide,  Magnesic  Oxide. 

CaO  CaO        Lime,  Calcium  Oxide,  Calcic  Oxide. 

Fe,Os  Fe,Os     Iron  Oxide,  Peroxide  of  Iron,  Sesquioxide  of  Iron, 

Ferric  Oxide. 

PO6  P,OS        Phosphoric    Acid,   Anhydrous   Phosphoric   Acid, 

Phosphoric   Anhydide,    Phosphorus    Pentox- 
ide,  Phosphoric  Oxide. 

SO,  SO8          Sulphuric  Acid,  Anhydrous  Sulphuric  Acid,  Sul- 

phuric   Anhydride,    Sulphur    Trioxide,    Sul- 
phuric Oxide. 

SiO,  SiO,         Silicic  Acid,  Anhydrous  Silicic  Acid,  Silicic  An- 

hydride,  Silicon  Dioxide,  Silicic  Oxide,  Silica 
Silex. 

CO,  CO,          Carbonic  Acid,  Anhydrous  Carbonic  Acid,  Car- 

bonic Anhydride,  Carbon  Dioxide,  Carbouie 
Dioxide. 


HOW  CROPS  GROW. 


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THE  ASH  OF  PLANTS. 


165 


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11  "  by  Way  &  Ogston. 
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NEL. 

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Way  &  Ogston. 
Fromberg. 
Letellier. 
W.  H.  Brewer. 
Stepf.f 
Bibra. 

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HOW  CROPS  GROW. 


1 

Ritter  &  Knop. 
Way  &  Ogston. 
.nalyses. 

not  Included  above. 

y  Scluilz  -  Fleeth,  and  1  by 
Metzdorff.  [Wolff. 
Walz. 
Herapath. 
Bretschneider. 
AVay  &  Ogston. 
others.* 
Analyses. 
"  [above, 
fses  by  Heiden  not  included 

y  Ritthausen. 
'  Bretschneider.  [berg. 
'  Bret  schiieider  &  Kiillen- 
off  man  u 
armrodt. 
Analyses. 

L  W. 

Average  of  9  Analyses. 
"  4  "  by 
"  5  "  " 
Lowest  percentage  in  9  A 
Highest  "  9 
j  Old  Analyses  by  Hertwig 

Average  of  39  Analyses. 
7  b 
8 
3 
5 
4 
3 
8 
Lowest  percentage  in  39  1 
Highest  "  39 
Av  rage  of  4  recent  Anal; 

ROOT. 

Average  of  40  Analyses. 
"  13  "  t 
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THE  ASH  OF  PLANTS. 


169 


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HOW  CEOPS  GKOW. 


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Grain*....  30 

12 

3 

46 

Straw...  13—27 

3 

7 

5 

LEGUMES— 

Kernel...    44 

7 

5 

35 

Straw...  27—11 

7 

25-39 

8 

ROOT  CROPS— 

Roots....    60 

3-9 

6—12 

8—18 

Tops....      37 

3—16 

10—35 

3—8 

GRASSES— 

In  flower..  33 

4 

8 

8 

THE  ASH  OF  PLANTS.  171 

The  composition  of  the  ash  of  a  number  of  ordinary 
crops  is  concisely  exhibited  in  the  subjoined  general  state- 
ment. 

Ma#-    jim*    Phosphor-  &,*,,„  Sulphur-  rj,,.,,.^., 

Alkalies,  nesia.  Lime"    ic  Acid.     Mlwa.  ic  Acid^    Chlorine. 
CEREALS— 

2  2.5  1 
50—70          2.5                 2 

14  2 

5  2—6  6—7 

1—4          5—12  3—9 

3  6-13  5—17 

35  4  5 

3.  Different  parts  of  any  plant  usually  exhibit  decided 
differences  in  the  composition  of  their  ash.  This  fact  is 
made  evident  by  a  comparison  of  the  figures  of  the  table 
above,  and  is  more  fully  illustrated  by  the  following  anal- 
yses of  the  parts  of  the  mature  oat-plant,  by  Arendt,  1  to 
6  (Die  Haferpflanze,  p.  107),  and  Norton,  7  to  9  (Am. 
Jour.  Sci.,  2  Ser.  3,  318). 

1  2  34  56789 

Lower  Middle    Upper    Lower   Upper  Ears.  Chaff.  Husk.  Kernel 
Stem.   Stem.     Stem.    Leaves.  Leaves.  husked. 

Potash 81.2       68.3        55.9        36.9      24.8        13.0) 

Soda 0.4         1.5          1.0          0.9        0.4          O.I)10-06      12-4      31-7 

Magnesia 2.1         3.6          3.9          3.8        3.9          8.9 1  2.3         8.6 

Lime 3.6         5.3          8.6        16.7      17.2          7.3  I   „  9         4.3         5.3 

Oxide  of  Iron....  1.0        0.0         0.2         2.7       0.5    trace  f  11"5         0.3        0.8 
Phosphoric  acid.  2.7         1.4         2.7         1.7       1.5       36.5  J  0.6       49.1 

Sulphuric  acid..  0.0         1.3         1.1         3.2       7.5         4.9       5.3         4.3        0.0 

Silica 4.1         9.3        20.4        34.0      41.8        26.0     68.0        74.1         1.8 

Chlorine 8.6       11.7          7.4          1.6        2.4          3.8       3.1          1.4        0.2 

The  results  of  Arendt  and  Norton  are  not  in  all  respects  strictly  com- 
parable, having  been  obtained  by  different  methods,  but  serve  well  to 
establish  the  fact  in  q  .icstion. 

We  see  from  the  above  figures  that  the  ash  of  the  lower 
stem  consists  chiefly  of  potash  (81%).  This  alkali  is  pre- 
dominant throughout  the  stem,  but  in  the  upper  parts, 
where  the  stem  is  not  covered  by  the  leaf  sheaths,  silica 
and  lime  occur  in  large  quantity.  In  the  ash  of  the  leaves, 
silica,  potash,  and  lime  are  the  principal  ingredients.  In 
the  chaff  and  husk,  silica  constitutes  three-fourths  of  the 
ash,  while  in  the  grain,  phosphoric  acid  appears  as  the  char- 

•Exclusive  of  husk* 


172  HOW  CHOPS  GROW, 

acteristic  ingredient,  existing  there  in  connection  with  a 
large  amount  of  potash  (32%)  and  considerable  magne- 
sia. Chlorine  acquires  its  maximum  (11.7%)  in  the  mid- 
dle stem,  but  in  the  kernel  is  present  in  small  quantity, 
while  sulphuric  acid  is  totally  wanting  in  the  lower  stem, 
and  most  abundant  in  the  upper  leaves. 

Again,  the  unequal  distribution  of  the  ingredients  of 
the  ash  is  exhibited  in  the  leaves  of  the  sugar-beet,  which 
have  been  investigated  by  Bretschneider  (  Hoff.  Jahresbe- 
riclit,  4,  89).  This  experimenter  divided  the  leaves  of  6 
sugar-beets  into  5  series  or  circles,  proceeding  from  the 
outer  and  older  leaves  inward.  He  examined  each  series 
separately  with  the  following  results: 

I.  II.  III.  IV.  V. 

Potash 18.7  25.9  32.8  37.4  50.3 

Soda 15.2  14.4  15.8  15.0  11.1 

Chloride  of  Sodium....  5.8  6.4  5.8  6.0  6.5 

Lime 24.2  19.2  18.2  15.8  4.7 

Magnesia 24.5  22.3  13.0  8.9  6.7 

Oxide  of  Iron 1.4  0.5  0.6  0.6  0.5 

Phosphoric  acid 3.3  4.8  5.8  8.4  12.7 

Sulphuric  acid 5.4  5.6  5.6  5.2  5.9 

Silica 1.5  0.8  2.7  2.1  1.5 

From  these  data  we  perceive  that  in  the  ash  of  the  leaves 
of  the  sugar-beet,  potash  and  phosphoric  acid  regularly 
and  rapidly  increase  in  relation  to  the  other  ingredients 
from  without  inward,  while  lime  and  magnesia  as  rapidly 
diminish  in  the  same  direction.  The  per  cent  of  the  othef 
ingredients,  viz.,  soda,  chlorine,  oxide  of  iron,  sulphuric 
acid,  and  silica,  remains  nearly  invariable  throughout. 

Another  illustration  is  furnished  by  the  following  anal- 
yes  of  the  ashes  of  the  various  parts  of  the  horse-chestnut 
tree  made  by  Wolff  (Ackerlau,  2.  Anf.,  134): 

Baric.  Wood.  Leaf-sterns.  Leaves.  Flower-stems.  Calyx. 

Potash 12.1  25.7  46.2  27.9  63.6  61.7 

Lime .76.8  42.9  21.7  29.3  9.3  12.3 

Magnesia 1.7  5.0  3.0  2.6  1.3  5.9 

Sulphuric  acid trace  trace         3.8  9.1  3.5  trace 

Phosphoric  acid 6.0  19.2  14.8  22.4  17.1  16.6 

Silica 1.1  2.6  1.0  4.9  0.7  1.7 

Chlorine 2.8  6.1  12.2  5.1  4,7  2.4 


THE  ASH  OF  PLANTS.  173 

Ripe  Fruit. 


Stamens.    Peta.lt.    Green  Fruit.    Kernel.    Green    Brown 

Shell.     Shell. 

Potash 60.7  61.2  58.7  61.7  75.9  54.6 

Lime 13.8  13.6  9.8  11.5  8.6  16.4 

Magnesia 3.1  3.8  2.4  0.6  1.1  2.4 

Sulphuric  acid  —  trace  trace  3.7  1.7  1.0  3.6 

Phosphoric  acid...  19.5  17.0  20.8  22.8  5.3  18.6 

Silica 0.7  1.5  0.9  0.2  0.6  0.8 

Chlorine 2.8  3-8  4.8  2.0  7.6  5.2 

4.  Similar  kinds  of  plants,  and  especially  the  same  parts 
of  similar  plants,  exhibit  a  close  general  agreement  in  the 
composition  of  their  ashes  ;  while  plants  which  are  un- 
like in  their  botanical  characters  are  also  unlike  in  the 
proportions  of  their  fixed  ingredients. 

The  three  plants,  wheat,  rye,  and  maize,  belong,  botan- 
ically  speaking,  to  the  same  natural  order,  graminece,  and 
the  ripe  kernels  yield  ashes  almost  identical  in  composi- 
tion. Barley  and  the  oat  are  also  graminaceous  plants, 
and  their  seeds  should  give  ashes  of  similar  composition. 
That  such  is  not  the  case  is  chiefly  due  to  the  fact,  that, 
unlike  the  wheat,  rye,  and  maize-kernel,  the  grains  of 
barley  and  oats  are  closely  invested  with  a  husk,  which 
forms  a  part  of  the  kernel  as  ordinarily  seen.  This  husk 
yields  an  ash  which  is  rich  in  silica,  and  we  can  only  prop- 
erly compare  barley  and  oats  with  wheat  and  rye,  when 
the  former  are  hulled,  or  the  ash  of  the  hulls  is  taken  out 
of  the  account.  There  are  varieties  of  both  oats  and  bar- 
ley, whose  husks  separate  from  the  kernel — the  so-called 
naked  or  skinless  oats  and  naked  or  skinless  barley — and 
the  ashes  of  these  grains  agree  quite  nearly  in  composi- 
tion with  those  of  wheat,  rye,  and  maize,  as  may  be  seen 
from  the  table  on  page  174. 

By  reference  to  the  table  (p.  166),  it  will  be  observed 
that  the  pea  and  bean  kernel,  together  with  the  allied 
vetch  and  lentil  (p.  171),  also  nearly  agree  in  ash-com- 
position. 

So,  too,  the  ashes  of  the  root-crops,  turnips,  carrots, 


174:  HOW  CROPS  GROW. 

and  beets,  exhibit  a  general  similarity  of  composition,  as 
may  be  seen  in  the  table  (p.  168-9). 


Potash  

Wheat. 
Average 
of 
seventy-nine 
Analyses. 
.....31.3 

Rye. 
Average 
of 
twenty-one 
Analyses. 
28.8 

Maize. 
Average 
of 
seven 
Analyses. 
27.7 

Skinless 
oats. 
Analysis 
by  Fr. 
Scliulze. 
33  4 

Skinles 
barleys. 
Analysis 
by  Fr. 
Schulze, 
35  9 

3.2 

4.3 

4.0 

1  0 

12.3 

11.6 

15  0 

11  8 

13  7 

Lime  

3.2 

3.9 

1.9 

36 

2  9 

0.7 

0.8 

1  0 

0  8 

0  7 

Phosphoric  acid. 

46.1 

45.6 

47.1 

46  9 

45  0 

1.2 

1.9 

1  7 

Silica  

1.9 

2.6 

2.1 

24 

0  7 

Chlorine... 

..  0.2 

0.7 

0.1 

The  seeds  of  the  oil-bearing  plants  likewise  constitute 
a  group  whose  members  agree  in  this  respect  (p.  170). 

5.  The  ash  of  the  same  species  of  plant  is  more  or  less 
variable  in  composition,  according  to  circumstances. 

The  conditions  that  have  already  been  noticed  as  in- 
fluencing the  proportion  of  ash  are  in  general  the  same 
that  affect  its  quality.  Of  these  we  may  specially  notice  : 

a.  The  stage  of  growth  of  the  plant. 

b.  The  vigor  of  its  development. 

c.  The  variety  of  the  plant  or  the  relative  development 
of  its  parts,  and 

d.  The  soil  or  the  supplies  of  food. 

a.  The  stage  of  growth.     The  facts  that  the  different 
parts  of  a  plant  yield  ashes  of  different  composition,  and 
that  the  different  stages  of  growth  are  marked  by  the 
development  of  new  organs  or  the  unequal  expansion  of 
those  already  formed,  are  sufficient  to  sustain  the  point 
now  in  question,  and  render  it  needless  to  cite  analytical 
evidence.     In  a  subsequent  chapter,  wherein  we  shall  at- 
tempt to  trace  some  of  the  various  steps  in  the  progress- 
ive development  of  the  plant,  numerous  illustrations  will 
be  adduced  (p.  241). 

b.  Vigor  of  development.     Arendt  (Die  Haferpflanze, 
p.  18)  selected  from  an  oat-field  a  number  of  plants  in 
blossom,  and  divided  them  into  three  parcels  :  1,  com- 


THE  ASH  OF  PLANTS.  175 

posed  of  very  vigorous  plants  ;  2,  of  medium  ;  and,  3,  of 
very  weak  plants.  He  analyzed  the  ashes  of  each  parcel, 
with  results  as  below  : 

123 

Silica 27.0  39.9  42.0 

Sulphuric  acid 4.8  4.1  5.6 

Phosphoric  acid 8.2  8.5  8.8 

Chlorine 6.7  5.8  4.7 

Oxide  of  Iron 0.4  0.5  1.0 

Lime 6.1  5.4  5.1 

Magnesia,  Potash  and  Soda. 45.3  34.3  30.4 

Here  we  notice  that  the  ash  of  the  weak  plants  con- 
tains 15  per  cent  less  of  alkalies,  and  15  per  cent  more  of 
silica,  than  that  of  the  vigorous  ones,  while  the  propor- 
tion of  the  other  ingredients  is  not  greatly  different. 

Zoeller  (Liebig's  Erndhrung  der  Vegetabilien,  p.  340) 
examined  the  ash  of  two  specimens  of  clover  which  grew 
on  the  same  soil  and  under  similar  circumstances,  save 
that  one,  from  being  shaded  by  a  tree,  was  less  fully  de- 
veloped than  the  other. 

Six  weeks  after  the  sowing  of  the  seed,  the  clover  was 
cut,  and  gave  the  following  results  on  partial  analysis  : 

Shaded  clover.  Unshaded  clover. 

Alkalies 54.9  36.2 

Lime 14.2  22.8 

Silica 5.5  12.4 

c.  The  variety  of  the  plant  or  the  relative  development 
of  its  parts  must  obviously  influence  the  composition  of 
the  ash  taken  as  a  whole,  since  the  parts  themselves  are 
unlike  in  composition. 

Herapath  (Qu.  Jour.  Chem.  Soc.,  II,  p.  20)  analyzed 
the  ashes  of  the  tubers  of  five  varieties  of  potatoes,  raised 
on  the  same  soil  and  under  precisely  similar  circum- 
stances. His  results  are  as  follows  : 

White  Prince's  Axbridge 

Apple.  Beauty.  Kidney.  Magpie.  Forty-fold. 

Potash 69.7  65.2  70.6  70.0  62.1 

Chloride  of  Sodium.. 2.5 

Lime 3.0  1.8  5.0  5.0  3.3 

Magnesia 6.5  5.5  5.0  2.1  3.5 

Phosphoric  acid 17.2  20.8  14.9  14.4  30.7 

Sulphuric  acid 3.6  6.0  4.3  7.5  7.9 

Silica 0.2  —  — 


176  SOW  CROPS  GROW. 

d.  The  soil,  or  the  supplies  of  food,  manures  included, 
have  the  greatest  influence  in  varying  the  proportions  of 
the  ash-ingredients  of  the  plant.  It  is  to  a  considerable 
degree  the  character  of  the  soil  which  determines  the 
vigor  of  the  plant  and  the  relative  development  of  its 
parts.  This  condition,  then,  to  a  certain  extent,  in- 
cludes those  already  noticed. 

It  is  well  known  that  oats  have  a  great  range  of  weight 
per  bushel,  being  nearly  twice  as  heavy,  when  grown  on 
rich  land,  as  when  gathered  from  a  sandy,  inferior  soil. 
According  to  the  agricultural  statistics  of  Scotland,  for 
the  year  1857  (Trans.  Highland  and  Ag.  Soc.,  1857-9, 
p.  213},  the  bushel  of  oats  produced  in  some  districts 
weighed  44  pounds  per  bushel,  while  in  other  districts  it 
was  as  low  as  35  pounds,  and  in  one  instance  but  24 
pounds  per  bushel.  Light  oats  have  a  thick  and  bulky 
husk,  and  an  ash-analysis  gives  a  result  quite  unlike  that 
of  good  oats.  Herapath  (Jour.  Roy.  Ag.  Society,  XI, 
p.  107)  has  published  analyses  of  light  oats  from  sandy 
soil,  the  yield  being  six  bushels  per  acre,  and  of  heavy 
oats  from  the  same  soil,  after  "warping,"*  where  the 
produce  was  64  bushels  per  acre.  Some  of  his  results, 
per  cent,  are  as  follows  : 

Light  oats.  Heavy  oatt. 

Potash 9.8  13.1 

Soda 4.6  7.2 

Lime .'....  6.8  4.2 

Phosphoric  acid 9.7  17.6 

Silica 56.5  45.6 

.  Wolff  (Jour,  fur  PraTct.  Chem.,  52,  p,  103)  has  anal- 
ysed the  ashes  of  several  plants,  cultivated  in  a  poor  soil, 
with  the  addition  of  various  mineral  fertilizers.  The  in- 
fluence of  the  added  substances  on  the  composition  of  the 
plant  is  very  striking.  The  following  figures  comprise 
his  results  on  the  ash  of  buckwheat  straw,  which  grew 

*  Thickly  covering  with  sediment  from  muddy  tide-water. 


THE  ASH  OP  PLANTS.  17? 

on  the  unmanured  soil,  and  on  the  same,  after  applica- 
tion of  the  substances  specified  below  : 

1234  56 

Unma-  Chloride  Nitrate  Carbonate  Sulphate  Carbonate 

nured.        of             of             of  of                of 

tedium,    potash,    potash,  magneria.      lime. 

Potash 31.7       21.6         39.6         40.5  28.2             23.9 

Chloride  of  potassium....  7.4       26.9           0.8           3.1  6.9              9.7 

Chloride  of  sodium 4.6         3.0           3.2           3.8  3.4              1.7 

Lime 15.7        14.0         12.8         11.6  14.1             18.6 

Magnesia 1.7         1.9          3.3          1.4  4.7              4.2 

Sulphuric  acid 4.7         2.8           2.7           4.3  7.1              3.5 

Phosphoric  acid 10.3         9.5          6.5          8.9  10.9            10.0 

Carbonic  acid 20.4       16.1         27.1         22.2  20.0            23.2 

Silica 3.6         4.2           4.2           4.2  4.8              5.2 


100.0       100.0        100.0        100.0         100.0  100.0 

It  is  seen  from  these  figures  that  all  the  applications 
employed  in  this  experiment  exerted  a  manifest  influ- 
ence, and,  in  general,  the  substance  added,  or  at  least  one 
of  its  ingredients,  is  found  in  the  plant  in  increased 
quantity. 

In  2,  chlorine,  but  not  sodium  ;  in  3  and  4,  potash  ; 
in  5,  sulphuric  acid  and  magnesia,  and  in  6,  lime,  are 
present  in  larger  proportion  than  in  the  ash  from  the 
unmanured  soil. 

6.  What  is  the  normal  composition  of  the  ash  of  a 
plant  ?  It  is  evident  from  the  foregoing  facts  and  con- 
siderations that  to  pronounce  upon  the  normal  composi- 
tion of  the  ash  of  a  plant,  or,  in  other  words,  to  ascer- 
tain what  ash-ingredients  and  what  proportions  of  them 
are  proper  to  any  species  of  plant  or  to  any  of  its  parts, 
is  a  matter  of  much  difficulty  and  uncertainty. 

The  best  that  can  be  done  is  to  adopt  the  average  of  a 
great  number  of  trustworthy  analyses  as  the  approximate 
expression  of  ash-composition.  From  such  data,  how- 
ever, we  are  still  unable  to  decide  what  are  the  abso- 
lutely essential,  and  what  are  really  accidental,  ingredi- 
ents, or  what  amount  of  any  given  ingredient  is  essential, 
and  to  what  extent  it  is  accidental.  Wolff,  who  appears 
to  have  first  suggested  that  a  part  of  the  ash  of  plants 


178  HOW  CROPS  GROW. 

may  be  accidental,  endeavored  to  approach  a  solution  of 
this  question  by  comparing  together  the  ashes  of  sam- 
ples of  the  same  plant,  cultivated  under  the  same  circum- 
stances in  all  respects,  save  that  they  were  supplied  with 
unequal  quantities  of  readily-available  ash-ingredients. 
The  analyses  of  the  ashes  of  buckwheat-stems,  just 
quoted,  belong  to  this  investigation.  Wolff  showed  that, 
by  assuming  the  presence  in  each  specimen  of  buckwheat- 
straw  of  a  certain  excess  of  certain  ingredients,  and  de- 
ducting the  same  from  the  total  ash,  the  residuary  ingre- 
dients closely  approximated  in  their  proportions  to  those 
observed  in  the  crop  which  grew  in  an  unmanured  soil. 
The  analyses  just  quoted  (p.  163)  are  here  "corrected" 
in  this  manner,  by  the  subtraction  of  a  certain  per  cent 
of  those  ingredients  which  in  each  case  were  furnished 
to  the  plant  by  the  fertilizer  applied  to  it.  The  num- 
bers of  the  analyses  correspond  with  those  on  the  previ- 
ous page. 

123456 

20  p.  c.  ZOp.c.  25 p.  c.  8.5  p.  e.  16.6  p.  c. 

Chloride  Carbonate  Carbonate  Sulphate  Carbonatet 

After  deduction                           of  of  of  of      ofcalc'mand 
of Nothing,  pptas-  potas-  potas-  magne-  magne- 
sium, sium.  sium.  slum.  sium. 

Potash 31.7         27.0  32.5  33.5  30.6  28.0 

Chloride  of  potassium.  7.4           9.1  1.0  3.9  7.4  11.3 

Chloride  of  sodium...  4.6           3.8  4.0  4.7  3.7  1.9 

Lime 15.7         17.3  16.0  14.5  15.3  14.6 

Magnesia 1.7          2.4  4.1  1.7  2.3  2.9 

Sulphuric  acid 4.7          3.5  3.4  5.4  2.1  4.1 

Phosphoric  acid 10.3         11.7  8.1  11.2  11.8  11.7 

Carbonic  acid 20.4         20.1  25.9  19.8  21.6  19.3 

Silica 3.6           5.2  5.2  5.3  5.2  6.1 

100.0        100.0         100.0       100.0  100.0  100.0 

The  correspondence  in  the  above  analyses  thus  "  cor- 
rected," already  tolerably  close,  might,  as  Wolff  remarks 
(loc.  cit.),  be  made  much  more  exact  by  a  further  correc- 
tion, in  which  the  quantities  of  the  two  most  variable  in- 
gredients, viz.,  chlorine  and  sulphuric  acid,  should  be 
reduced  to  uniformity,  and  the  analyses  then  be  recalcu- 
lated to  per  cent. 


THE  ASH  OF  PLANTS.  179 

In  the  first  place,  however,  we  are  not  warranted 
in  assuming  that  the  "excess"  of  potassium  chloride, 
potassium  carbonate,  etc.,  deducted  in  the  above  analyses 
respectively,  was  all  accidental  and  unnecessary  to  the 
plant,  for,  under  the  influence  of  an  increased  amount  of 
a  nutritive  ingredient,  the  plant  may  not  only  mechani- 
cally contain  more,  but  may  chemically  employ  more  in 
the  vegetative  processes.  It  is  well  proved  that  vegeta- 
tion, grown  under  the  influence  of  large  supplies  of  nitro- 
genous manures,  contains  an  increased  proportion  of 
truly  assimilated  nitrogen  as  albuminoids,  amido-acids, 
etc.  The  same  may  be  equally  true  of  the  various  ash- 
ingredients. 

Again,  in  the  second  place,  we  cannot  say  that  in  any 
instance  the  minimum  quantity  of  any  ingredient  neces- 
sary to  the  vegetative  acts  is  present,  and  no  more. 

It  must  be  remarked  that  these  great  variations  are 
only  seen  when  we  compare  together  plants  produced  on 
poor  soils,  i.  e.,  on  those  which  are  relatively  deficient  in 
some  one  or  several  ingredients.  If  a  fertile  soil  had 
been  employed  to  support  the  buckwheat  plants  in  these 
trials,  we  should  doubtless  have  had  a  very  different 
result. 

In  1859,  Metzdorf  ( Wilda's  CentralUatt,  1862,  II,  p. 
367)  analysed  the  ashes  of  eight  samples  of  the  red- 
onion  potato,  grown  on  the  same  field  in  Silesia,  but  dif- 
ferently manured. 

Without  copying  the  analyses,  we  may  state  some  of 
the  most  striking  results.  The  extreme  range  of  varia- 
tion in  potash  was  5£  per  cent.  The  ash  containing  the 
highest  percentage  of  potash  was  not,  however,  obtained 
from  potatoes  that  had  been  manured  with  50  pounds  of 
this  substance,  but  from  a  parcel  to  which  had  been  ap- 
plied a  poudrette  containing  less  than  three  pounds  of 
potash  for  the  quantity  used. 

The  unmanured  potatoes  were  relatively  the  richest  in 


180  HOW  CROPS  GROW, 

lime,  phosphoric  acid,  and  sulphuric  aeid,  although  sev- 
eral parcels  were  copiously  treated  with  manures  contain- 
ing considerable  quantities  of  these  substances.  These 
facts  are  of  great  interest  in  reference  to  the  theory  of 
the  action  of  manures. 

7.  To  what  extent  is  each  ash-ingredient  essential, 
and  how  far  may  it  be  accidental  ?  Before  chemical 
analysis  had  arrived  at  much  perfection,  it  was  believed 
that  the  ashes  of  the  plant  were  either  unessential  to 
growth,  or  else  were  the  products  of  growth — were  gener- 
ated by  the  plant. 

Since  the  substances  found  in  ashes  are  universally  dis- 
tributed over  the  earth's  surface,  and  are  invariably  pres- 
ent in  all  soils,  it  is  not  possible,  by  analysis  of  the  ash 
of  plants  growing  under  natural  conditions,  to  decide 
whether  any  or  several  of  their  ingredients  are  indispen- 
sable to  vegetative  life.  For  this  purpose  it  is  necessary 
to  institute  experimental  inquiries,  and  these  have  been 
prosecuted  with  great  painstaking,  and  with  highly  val- 
uable results. 

Experiments  in  Artificial  Soils. — The  Prince  Salm- 
Horstmar,  of  Germany,  was  one  of  the  first  and  most 
laborious  students  of  this  question.  His  plan  of  experi- 
ment was  the  following  :  The  seeds  of  a  plant  were  sown 
in  a  soil-like  medium  (sugar-charcoal,  pulverized  quartz, 
purified  sand)  which  was  as  thoroughly  as  possible  freed 
from  the  substance  whose  special  influence  on  growth 
was  the  subject  of  study.  All  other  substances  presum- 
ably necessary,  and.  all  the  usual  external  conditions  of 
growth  (light,  warmth,  moisture,  etc.),  were  supplied. 

The  results  of  195  trials  thus  made  with  oats,  wheat, 
barley,  and  colza,  subjected  to  the  influence  of  a  great 
variety  of  artificial  mixtures,  have  been  described,  the 
most  important  of  which  will  shortly  be  given. 

Experiments  in  Solutions. — Water-Culture. — 
Sachs,  W.  Knop,  Stohmann,  Nobbe,  Siegert,  and  others 


THE  ASH  OF  PLAKTS. 


181 


have  likewise  studied  this  subject.  Their  method  was 
like  that  of  Prince  Salm-Horstmar,  except  that  the  plants 
were  made  to  germinate  and  grow  independently  of  any 
soil;  and,  throughout  the  experiment,  had  their  roots  im- 
mersed in  water,  containing  in  solution  or  suspension  the 
substances  whose  action  was  to  be  observed. 

Water-Culture  has  recently  contributed  so  much  to  our 
knowledge  of  the  conditions  of  vegetable  growth,  that 
some  account  of  the  mode  of  conducting  it  may  be  prop- 
erly given  in  this  place.  Cause  a  num- 
ber of  seeds  of  the  plant  it  is  desired  to 
experiment  upon  to  germinate  in  moist 
blotting-paper,  and,  when  the  roots  have 
become  an  inch  or  two  in  length,  select 
the  strongest  seedlings,  and  support 
them  so  that  the  roots  shall  be  immersed 
in  water,  while  the  seeds  themselves 
shall  be  just  above  the  surface  of  the 
liquid. 

For  this  purpose,  in  case  of  a  single 
maize  plant,  for  example,  provide  a 
quart  cylinder  or  bottle  with  a  wide 
mouth,  to  which  a  cork  is  fitted,  as  in 
Fig.  22.  Cut  a  vertical  notch  in  the 
cork  to  its  center,  and  fix  therein  the 
stem  of  the  seedling  by  packing  with 
cotton.  The  cork  thus  serves  as  a  sup- 
port of  the  plant.  Fill  the  jar  with  pure 
water  to  such  a  height  that  when  the 
cork  is  brought  to  its  place,  the  seed,  8, 
shall  be  a  little  above  the  liquid.  If 
the  endosperm  or  cotyledons  dip  into  the  water,  they 
will  speedily  mould  and  rot ;  they  require,  however,  to  be 
kept  in  a  moist  atmosphere.  Thus  arranged,  suitable 
warmth,  ventilation,  and  illumination  alone  are  requi- 
site to  continue  the  growth  until  the  nutriment  of  the  seed 


Fig.  281 


182  HOW  CHOPS  GBOW. 

is  nearly  exhausted.  As  regards  illumination,  this  should 
be  as  full  as  possible,  for  the  foliage  ;  but  the  roots  should 
be  protected  from  it,  by  enclosing  the  vessel  in  a  shield  of 
black  paper,  as,  otherwise,  minute  parasitic  algae  would 
in  time  develop  upon  the  roots,  and  disturb  their  functions. 
For  the  first  days  of  growth,  pure  distilled  water  may  ad- 
vantageously surround  the  roots,  but,  when  the  first  green 
leaf  appears,  they  should  be  placed  in  the  solution  whose 
nutritive  power  is  to  be  tested.  The  temperature  should 
be  properly  proportioned  to  the  light,  in  imitation  of  what 
is  observed  in  the  skillful  management  of  conservatory  or 
house-plants. 

The  experimenter  should  first  learn  how  to  produce 
large  and  well-developed  plants  by  aid  of  an  appropriate 
liquid,  before  attempting  the  investigation  of  other  prob- 
lems. For  this  purpose,  a  solution  or  mixture  must  be 
prepared,  containing  in  proper  proportions  all  that  the 
plant  requires,  save  what  it  can  derive  from  the  atmos- 
phere. The  experience  of  Nobbe  and  Siegert,  Knop, 
Wolff,  and  others,*  supplies  valuable  information  on  this 
point.  Wolff  has  obtained  striking  results  with  a  variety 
of  plants  in  using  a  solution  made  essentially  as  follows: 

Place  20  grams  of  the  fine  powder  of  well-burned  bones 
with  a  half  pint  of  water  in  a  large  glass  flask,  heat  to  boil- 
ing, and  add  nitric  acid  cautiously  in  quantity  just  suffi- 
cient to  dissolve  the  bone-ash.  In  order  to  remove  any 
injurious  excess  of  nitric  acid,  pour  into  the  boiling  liq- 
uid a  solution  of  pure  potassium  carbonate  until  a  slight 
permanent  turbidity  is  produced;  then  add  11  grams  of 
potassium  nitrate,  7  grams  of  crystallized  magnesium  sul- 
phate, and  3  grams  of  potassium  chloride,  with  water 
enough  to  make  the  solution  up  to  the  bulk  of  one  liter. 

Wolff's  solution,  thus  prepared,  contains  in  1000  parts 
as  follows,  exclusive  of  iron: 

*  See  especially  Tollens  (Hennebery's  Jour.filr  Landurlrthschaft,  1882,  p. 
637)  for  full  and  concise  instructions. 


THE  ASH  OF  PLANTS.  183 


Phosphoric  acid 8.2 

Lime 10.5 

Potash 9.1 

Magnesia 1.4 

Sulphuric  acid 2.2 

Chlorine 0.9 

Nitric  acid . . .  .29.7 


Solid  Matters 62 

Water 938 

1000 

For  use,  dilute  15  or  20  c.  c.  of  the  above  solution  with 
water  to  the  bulk  of  a  liter  and  add  one  or  two  drops  of 
strong  solution  of  ferric  chloride. 

The  solution  should  be  changed  at  first  every  week,  and, 
as  the  plants  acquire  greater  size,  their  roots  should  be 
transferred  to  a  larger  vessel  filled  with  solution  of  the 
same  strength,  and  the  latter  changed  every  5  or  3  days. 

It  is  important  that  the  water  which  escapes  from  the 
,  jar  by  evaporation  and  by  transpiration  through  the  plant 
should  be  daily  or  oftener  replaced,  by  filling  it  with  pure 
water  up  to  the  original  level.  The  solution,  whose  prep- 
aration has  been  described,  may  be  turbid  from  the  sepa- 
ration of  a  little  calcium  sulphate  before  the  last  dilution, 
as  well  as  from  the  precipitation  of  phosphate  of  iron  on 
adding  ferric  chloride.  The  former  deposit  may  be  dis- 
solved, though  this  is  not  needful;  the  latter  will  not  dis- 
solve, and  should  be  occasionally  put  into  suspension  by 
stirring  the  liquid.  When  the  plant  is  half  grown,  fur- 
ther addition  of  iron  is  unnecessary. 

In  this  manner,  and  with  this  solution,  Wolff  produced 
a  maize  plant  five  and  three  quarters  feet  high,  and  equal 
in  every  respect,  as  regards  size,  to  plants  from  similar 
seed,  cultivated  in  the  field.  The  ears  were  not,  however, 
fully  developed  when  the  experiment  was  interrupted  by 
the  plant  becoming  unhealthy. 

With  the  oat  his  success  was  better.  Four  plants  were 
brought  to  maturity,  having  46  stems  and  1535  well-de- 
veloped seeds.  (Vs.  St.,  VIII,  pp.190-215.) 


184  HOW  CEOPS  GROW. 

In  similar  experiments,  Nobbe  obtained  buckwheat 
plants,  six  to  seven  feet  high,  bearing  three  hundred 
plump  and  perfect  seeds,  and  barley  stools  with  twenty 
grain-bearing  stalks.  (Vs.  St.,  VII,  p.  72.) 

In  water-culture  the  composition  of  the  solution  is  suf- 
fering continual  alteration,  from  the  fact  that  the  plant 
makes,  to  a  certain  extent,  a  selection  of  the  matters  pre- 
sented to  it,  and  does  not  necessarily  absorb  them  in  the 
proportions  in  which  they  originally  existed.  In  this 
way,  disturbances  arise  which  impede  or  become  fatal  to 
growth.  In  the  early  experiments  of  Sachs  and  Knop, 
in  1860,  they  frequently  observed  that  their  solutions 
suddenly  acquired  the  odor  of  hydrogen  sulphide,  and 
black  iron  sulphide  formed  upon  the  roots,  in  consequence 
of  which  they  were  shortly  destroyed.  This  reduction  of 
a  sulphate  to  a  sulphide  takes  place  only  in  an  alkaline 
liquid,  and  Stohmann  was  the  first  to  notice  that  an  acid 
liquid  might  be  made  alkaline  by  the  action  of  living 
roots.  The  plant,  in  fact,  has  the  power  to  decompose 
salts,  and  by  appropriating  the  acids  more  abundantly 
than  the  bases,  the  latter  accumulate  in  the  solution  in 
the  free  state,  or  as  carbonates  with  alkaline  properties. 

To  prevent  the  reduction  of  sulphates,  the  solution 
must  be  kept  slightly  acid,  if  needful,  by  addition  of  a 
very  little  free  nitric  acid,  and,  if  the  roots  blacken,  they 
must  be  washed  with  a  dilute  acid,  and,  after  rinsing  with 
water,  must  be  transferred  to  a  fresh  solution. 

On  the  other  hand,  Kiihn  has  shown  that  when  am 
monium  chloride  is  employed  to  supply  maize  with  nitro- 
gen, this  salt  is  decomposed,  its  ammonia  assimilated,  and 
its  chlorine,  which  the  plant  cannot  use,  accumulates  in 
the  solution  in  the  form  of  hydrochloric  acid  to  such  an 
extent  as  to  prove  fatal  to  the  plant  (Henneberg' s  Journal, 
1864,  pp.  116  and  135).  Such  disturbances  are  avoided  by 
employing  large  volumes  of  solution,  and  by  frequently 
renewing  them, 


THE  ASH  OF  PLANTS.  185 

The  concentration  of  the  solution  is  by  no  means  a 
matter  of  indifference.  While  certain  aquatic  plants,  as 
sea-weeds,  are  naturally  adapted  to  strong  saline  solutions, 
agricultural  land-plants  rarely  succeed  well  in  water  cul- 
ture, when  the  liquid  contains  more  than  ^^  of  solid 
matters,  and  will  thrive  in  considerably  weaker  solutions. 

Simple  well-water  is  often  rich  enough  in  plant-food  to 
nourish  vegetation  perfectly,  provided  it  be  renewed  suffi- 
ciently often.  Sachs's  earliest  experiments  were  made 
with  well-water. 

Birner  and  Lucanus,  in  1864  ( Vs.  /Stf.,VIII,  154),  raised 
oat-plants  in  well-water,  which  in  respect  to  entire  weight 
were  more  than  half  as  heavy  as  plants  that  grew  simul- 
taneously in  garden  soil,  and,  as  regards  seed-production, 
fully  equalled  the  latter.  The  well-water  employed  con- 
tained but  sisW  °f  dissolved  matters,  or  in  100,000  parts: 

Potash 2.10 

Lime 15.10 

Magnesia 1.50 

Phosphoric  acid 0.16 

Sulphuric  acid 7.50 

Nitric  acid 6.00 

Silica,  Chlorine,  Oxide  of  iron traces 


100,000 

On  the  other  hand,  too  great  dilution  is  fatal  to  growth. 
Nobbe  (Vs.  St.,  VIII,  337)  found  that  in  a  solution  con- 
taining but  T<TO (T7  °f  solid  matters,  which  was  continually 
renewed,  barley  made  no  progress  beyond  germination, 
and  a  buckwheat  plant,  which  at  first  grew  rapidly,  was 
soon  arrested  in  its  development,  and  yielded  but  a  few 
ripe  seeds,  and  but  1. 746  grm.  of  total  dry  matter. 

"While  water-culture  does  not  provide  all  the  normal 
conditions  for  the  growth  of  land  plants — the  soil  having 
important  functions  that  cannot  be  enacted  by  any  liquid 
medium — it  is  a  method  of  producing  highly-developed 
plants,  under  circumstances  which  admit  of  accurate  cou- 


186  HOW  CEOPS  GROW. 

trol  and  great  variety  of  alteration,  and  is,  therefore,  of 
the  utmost  value  in  vegetable  physiology.  It  has  taught 
important  facts  which  no  other  means  of  study  could  re- 
veal, and  promises  to  enrich  our  knowledge  in  a  still 
more  eminent  degree. 

Potassium,  Calcium,  and  Magnesium  as  soluble 
Salts,  Phosphorus  as  Phosphates  and  Sulphur  as 
Sulphates,  are  absolutely  necessary  for  the  life  of 
Agricultural  Plants,  as  is  demonstrated  by  all  the  ex- 
periments hitherto  made  for  studying  their  influence. 

It  is  impossible  to  recount  here  in  detail  the  evidence 
to  this  effect  that  is  furnished  by  the  investigations  of 
Salm-Horstmar,  Sachs,  Knop,  Nobbe,  Birner  and  Luca- 
nus,  and  others  ( Vs.  St.,  VIII,  p.  128-161). 

Some  of  the  experimental  proof  of  this  statement  is 
strikingly  exhibited  by  the  figures  on  Plate  I,  copied 
from  Nobbe,  showing  results  of  the  water-culture  of 
buckwheat  in  normal  nutritive  solutions  and  in  solutions 
variously  deficient. 

Is  Sodium  Essential  for  Agricultural  Plants? 
This  question  has  occasioned  much  discussion.  A  glance 
at  the  table  of  ash-analyses  (pp.  164-170)  will  show  that 
the  range  of  variation  is  very  great  as  regards  this  alkali- 
metal.  The  older  analysts  often  reported  a  considerable 
proportion  of  sodium  oxide,  even  20%  or  more,  in  the  ash 
of  seeds  and  grains.  In  most  of  the  analyses,  however, 
sodium  oxide  is  given  in  much  smaller  quantity.  The 
average  in  the  ashes  of  the  grains  is  less  than  3  per  cent, 
and  in  not  a  few  of  the  analyses  it  is  entirely  wanting. 

In  the  older  analyses  of  other  classes  of  agricultural 
plants,  especially  in  root  crops,  similarly  great  variations 
occur.  Some  uncertainty  exists  as  to  these  older  data,  for 
the  reason  that  the  estimation  of  sodium  by  the  processes 
customarily  employed  is  liable  to  great  inaccuracy,  espe- 
cially with  the  inexperienced  analyst.  On  the  one  hand, 
it  is  not  or  was  not  easy  to  detect,  much  less  to  estimate, 


THE  ASH  OF  PLANTS.  187 

minute  traces  of  sodium  when  mixed  with  much  potassi- 
um ;  while,  on  the  other  hand,  sodium,  if  present  to  the 
extent  of  a  per  cent  or  more,  is  very  liable  to  be  estimated 
too  high.  It  has  therefore  been  doubted  if  these  high 
percentages  in  the  ash  of  grains  are  correct. 

Again,  the  processes  formerly  employed  for  preparing 
the  ash  of  plants  for  analysis  were  such  as,  by  too  elevated 
and  prolonged  heating,  might  easily  occasion  a  partial 
or  total  expulsion  of  sodium  from  a  material  which  prop- 
erly should  contain  it,  and  we  may  hence  be  in  doubt 
whether  the  older  analyses,  in  which  sodium  is  not  men- 
tioned, are  to  be  altogether  depended  upon. 

The  later  analyses,  especially  those  by  Bibra,  Zoeller, 
Arendt,  Bretsclmeider,  Ritthausen,  and  others,  who  have 
employed  well-selected  and  carefully-cleaned  materials  for 
their  investigations,  and  who  have  been  aware  of  all  the 
various  sources  of  error  incident  to  such  analyses,  must 
therefore  be  appealed  to  in  this  discussion.  From  these 
recent  analyses  we  are  led  to  precisely  the  same  conclu- 
sions as  were  warranted  by  the  older  investigations.  Here 
follows  a  statement  of  the  range  of  percentages  of  sodium 
oxide  in  the  ash  of  several  field  crops,  according  to  the 
newest  analyses: 

SODIUM  OXIDE  (SODA)  IN  LATER  ASH-ANALYSES. 

Ash  of  Wheat  kernel,     none,    Bibra,  to      5%     Bibra. 

0.28%     Lawes&  Gilbert,"   1.18% 

Potato  tuber,      none,  j  ^etoforff,  "       4%     Wolff" 

Barlev   kernel     I    l%  Blbra<  «        ROIL  { Bibra. 

ielf    \   2%  Zoeller,  b%{veltmann. 

"  "  "  7%    Zoeller. 

s*.,!r-ir  hPot  J   4%  Ritthausen,  "  29.8%    Ritthausen. 

)   7%  Bretsclmeider,  "  16.6%   Bretsehneider. 

Turnip  root,  7.7%  Anderson,  "   17.1%   Anderson. 

Although,  as  just  indicated,  sodium  in  some  instances 
Las  been  found  wanting  in  the  wheat  kernel  and  in  po- 
tato tubers,  it  is  not  certain  that  it  was  absent  from  other 
parts  of  the  same  plants,  nor  has  it  been  proved  that 
sodium  is  wanting  in  any  entire  plant  which  has  grown 
on  a  natural  soil. 


188  HOW  CROPS  GROW. 

Weinhold  found  in  the  ash  of  the  stem  and  leaves  of 
the  common  live-for-ever  (Sedum  telephium)  no  trace  01 
sodium  detectable  by  ordinary  means  ;  while  in  the  ash 
of  the  roots  of  the  same  plant  there  occurred  1.8  per 
cent  of  its  oxide  ( Vs.  St.,  IV,  p.  190). 

It  is  possible  then  that,  in  the  above  instances,  so- 
dium really  existed  in  the  plants,  though  not  in  those 
parts  which  were  subjected  to  analysis.  It  should  be 
added  that  in  ordinary  analyses,  where  sodium  is  stated 
to  be  absent,  ft  is  simply  implied  that  it  is  present,  if  at 
all,  in  too  small  a  quantity  to  admit  of  determining  by 
the  usual  method,  while  in  reality  a  minute  amount  may 
be  present  in  all  such  cases.* 

The  final  result  of  all  the  analytical  investigations 
hitherto  made,  with  regard  to  cultivated  agricultural 
plants,  then,  is  that  sodium  is  an  extremely  variable  in- 
gredient of  the  ash  of  plants,  and  though  generally  pres- 
ent in  some  proportion,  and  often  in  large  proportion, 
has  been  observed  to  be  absent  in  weighable  quantity  in 
the  seeds  of  grains  and  in  the  tubers  of  potatoes. 

Salm-Horstmar,  Stohmann,  Knop,  and  Nobbe  &  Sie- 
gert  have  contributed  experimental  evidence  bearing  on 
this  question. 

The  investigations  of  Salm-Horstmar  were  made  with 
great  nicety,  and  especial  attention  was  bestowed  on  the 
influence  of  very  minute  quantities  of  the  various  sub- 
stances employed.  He  gives  as  the  result  of  numerous 
experiments,  that,  for  wheat,  oats,  and  barley,  in  the 
early  vegetative  stages  of  growth,  Sodium,  while  advan- 
tageous, is  not  essential,  but  that  for  the  perfection  of 
fruit  an  appreciable  though  minute  quantity  of  this  ele- 
ment is  indispensable.  ( Versuche  und  Resultate  tiber 
die  Nalirung  der  Pflanzen,  pp.  12,  27,  29,  36.) 

*The  methods  of  spectral  analysis,  by  which  winshisTn  of  a  grain  of 
sodium  oxide  may  be  detected,  demonstrate  this  element  to  be  so  uni- 
versally distributed!  that  it  is  next  to  impossible  to  find  or  to  prepare 
anything  that  is  free  from  it. 


THE  ASH  OP  PLANTS.  180 

Stohmann's  single  experiment  led  to  the  similar  con- 
clusion, that  maize  may  dispense  with  sodium  in  the 
earlier  stages  of  its  growth,  but  requires  it  for  a  full 
development.  (Henneberg's  Jour,  fur  Landwirthschaft, 
1862,  p.  25.) 

Knop,  on  the  other  hand,  succeeded  in  bringing  the 
maize  plant  to  full  perfection  of  parts,  if  not  of  size,  in  a 
solution  which  was  intended  and  asserted  to  contain  no 
sodium.  (Vs.  St.,  Ill,  p.  301.)  Nobbe  &  Siegert  came 
to  the  same  results  in  similar  trials  with  buckwheat. 
Vs.  St.,  IV,  p.  339.) 

Later  trials  by  Nobbe,  Schroder  and  Erdmann,  and  by 
others,  confirm  the  conclusion  that  sodium  may  be  nearly 
or  altogether  dispensed  with  by  plants. 

The  buckwheat  represented  in  Plate  I  vegetated  for  3 
months  in  solutions  as  free  as  possible  from  sodium,  with 
the  exception  of  VI,  in  which  sodium  was  substituted 
for  potassium. 

The  experiments  of  Knop,  Nbbbe,  Siegert  and  others, 
while  they  prove  that  much  sodium  is  not  needful  to 
maize  and  buckwheat,  do  not,  however,  satisfactorily 
demonstrate  that  a  little  sodium  is  not  necessary,  because 
the  solutions  in  which  the  roots  of  the  plants  were  im 
mersed  stood  for  months  in  glass  vessels,  and  could 
scarcely  fail  to  dissolve  some  sodium  from  the  glass. 
Again,  slight  impurity  of  the  substances  which  were  em- 
ployed in  making  the  solution  could  scarcely  be  avoided 
without  extraordinary  precautions,  and,  finally,  the  seeds 
of  these  plants  might  originally  have  contained  enough 
sodium  to  supply  this  substance  to  the  plants  in  appre- 
ciable quantity. 

To  sum  up,  it  appears  from  all  the  facts  before  us  : 

1.  That  sodium  is  never  totally  absent  from  plants, 
and  that, 

2.  If  indispensable,  but  a  minute  amount  of  it  is 
requisite. 


190  HOW  CROPS  GROW. 

3.  That  the  foliage  and  succulent  portions  of  the  plant 
may  include  a  considerable  amount  of  sodium  that  is  not 
necessary  to  the  plant ;  that  is,  in  other  words,  accidental. 

Can  Sodium  replace  Potassium  ? — The  close  simi- 
larity of  potassium  and  sodium,  and  the  variable  quanti- 
ties in  which  the  latter  especially  is  met  with  in  plants, 
have  led  to  the  assumption  that  one  of  these  alkali-metals 
can  take  the  place  of  the  other. 

Salm-Horstmar  and  Knop  &  Schreber  first  demon- 
etrated  that  sodium  cannot  entirely  take  the  place  of 
potassium — that,  in  other  words,  potassium  is  indispen- 
sable to  plant  life.  Plate  I,  VI,  shows  the  development 
of  buckwheat  during  3  months,  in  Nobbe,  Schroder  & 
Erdmann's  water-cultures,  when,  in  a  normal  nutritive 
solution,  potassium  is  substituted  by  sodium,  as  com- 
pletely as  is  practicable. 

Cameron  concluded,  from  a  series  of  experiments  which 
it  is  unnecessary  to  describe,  that,  under  natural  condi- 
tions, sodium  may  partially  replace  potassium.  A  partial 
replacement  of  this  kind  would  appear  to  be  indicated 
by  many  facts.  Thus,  Herapath  has  made  two  analyses 
of  asparagus,  one  of  the  wild,  the  other  of  the  culti- 
vated plant,  both  gathered  in  flower.  The  former  was 
rich  in  sodium,  the  latter  almost  destitute  of  this  sub- 
stance, but  contained  correspondingly  more  potassium. 
Two  analyses  of  the  ash  of  the  beet,  one  by  Wolff  (1),  the 
other  by  Way  (2),  exhibit  similar  differences  : 

Asparagus.  Field  Beet. 

Wild.  Cultivated.  1.  2. 

Potassium  oxide 18.8  50.5  57.0  25.1 

Sodium  oxide 16.2  trace  7.3  34.1 

Calcium  oxide ...28.1  21.3  5.8  2.2 

Magnesium  oxide 1.5  4.0  2.1 

Chlorine 16.5  8.3  4.9  34.8 

Sulphur  trioxide 9.2  4.5  3.5  3.6 

Phosphorus  pentoxide  12.8  12.4  12.9  1.9 

Silica 1.0  3.7  3.7  1.7 

These  results  go  to  show — it  being  assumed  that  only  a 
very  minute  amount  of  sodium,  if  any,  is  absolutely  nee- 


THE  ASH  OF  PLANTS.  191 

essary  to  plant-life — that  the  sodium  which  appears  to 
replace  potassium  is  accidental,  and  that  the  replaced 
potassium  is  accidental  also,  or  in  excess  above  what  is 
really  needed  by  the  plant,  and  leaves  us  to  infer  that  the 
quantity  of  these  bodies  absorbed  depends  to  some  ex- 
tent on  the  composition  of  the  soil,  and  is  to  the  same 
degree  independent  of  the  wants  of  vegetation. 

Alkalies  in  Strand  and  Marine  Plants. — The 
above  conclusions  apply  also  to  plants  which  most  com- 
monly grow  near  or  in  salt  water.  Asparagus,  the  beet 
and  carrot,  though  native  to  saline  shores,  are  easily  ca- 
pable of  inland  cultivation,  and  indeed  grow  wild  in  com- 
parative absence  of  sodium  compounds. 

The  common  saltworts,  Salsola,  and  the  samphire, 
Salicornia,  are  plants  which,  unlike  those  just  men- 
tioned, seldom  stray  inland.  Gobel,  who  has  analyzed 
these  plants  as  occurring  on  the  Caspian  steppes,  found 
in  the  soluble  part  of  the  ash  of  the  Salsola  brachiata 
4.8  per  cent  of  potassium  oxide,  and  30.3  per  cent  of 
sodium  oxide,  and  in  the  Salicornia  herbacea  2.6  per 
cent  of  potassium  oxide  and  36.4  per  cent  of  sodium 
oxide,  the  sodium  oxide  constituting  in  the  first  instance 
no  less  than  ^  and  in  the  latter  ^  of  the  entire 
weight,  not  of  the  ash,  but  of  the  air-dry  plant.  Potas- 
sium is  never  absent  from  these  forms  of  vegetation. 
(Agricultur-Chemie,  3te  Auf.y  p.  66.) 

According  to  Cadet  (Liebig's  ErndJirung  der  Veg., 
p.  100),  the  seeds  of  the  Salsola  kali,  sown  in  common 
garden  soil,  gave  a  plant  which  contained  both  sodium 
and  potassium ;  from  the  seeds  of  this,  sown  also  in 
garden  soil,  grew  plants  in  which  only  potassium-salts 
with  traces  of  sodium  could  be  found.  These  strand- 
plants  are  occasionally  found  at  a  distance  from  salt- 
shores,  and  their  growth  as  strand-plants  appears  to  be 
due  to  their  capacity  for  flourishing  in  spite  of  salt,  and 
not  from  their  requiring  it.  (Hoffmann,  Vs.  St.,  XIII, 
p.  295.) 


192  HOW  CROPS  GBOW. 

Another  class  of  plants — the  sea- weeds  (algce) — de- 
rive their  nutriment  exclusively  from  the  sea- water  in 
which  they  are  immersed.  Though  the  quantity  of  po- 
tassium in  sea-water  is  but  ^  that  of  the  sodium,  it  is 
yet  a  fact,  as  shown  by  the  analyses  of  Forchhammer 
(Jour,  fur  Prakt.  Chem.,  36,  p.  391)  and  Anderson 
(Trans.  High,  and  Ag.  Soc.,  1855-7,  p.  349)  that  the 
ash  of  sea-weeds  is,  in  general,  as  rich,  or  even  richer,  in 
potassium  than  in  sodium.  In  14  analyses,  by  Forch- 
hammer, the  average  amount  of  sodium  in  the  dry  weed 
was  3.1  per  cent;  that  of  potassium  2.5  per  cent.  In 
Anderson's  results  the  percentage  of  potassium  is  inva- 
riably higher  than  that  of  sodium.* 

Analogy  with  land-plants  would  lead  to  the  inference 
that  the  sodium  of  the  sea-weeds  is  in  a  great  degree  ac- 
cidental. In  fact,  Fucus  vesiculosis  and  Zygogonium  sal~ 
inum  have  been  observed  to  flourish  in  fresh  water. 
(Vs.  St.,  XIII,  p.  295.) 

Iron  is  Essential  to  Plants. — It  is  abundantly 
proved  that  a  minute  quantity  of  ferric  oxide,  Fe208,  is 
essential  to  growth,  though  the  agricultural  plant  may 
be  perfect  if  provided  with  so  little  as  to  be  discoverable 
in  its  ash  only  by  sensitive  tests.  According  to  Salm- 
Horstmar,  ferrous  oxide,  FeO,  is  indispensable  to  the 
colza  plant.  (Versuche,  etc.,  p.  35.)  Knop  asserts  that 
maize,  which  refuses  to  grow  in  entire  absence  of  iron, 
flourishes  when  ferric  phosphate,  which  is  exceedingly 
insoluble,  is  simply  suspended  in  the  solution  that  bathes 
its  roots  for  the  first  four  weeks  only  of  the  growth  of 
the  plant.  (  Vs.  St.,  V,  p.  101.) 

"We  find  that  the  quantity  of  ferric  oxide  given  in  the 
analyses  of  the  ashes  of  agricultural  plants  is  small,  being 
usually  less  than  one  per  cent. 

Here,  too,  considerable  variations  are  observed.     In 

*  Doubtless  due  to  the  fact  that  the  material  used  by  Anderson  was 
freed  by  washing  from  adhering  common  salt. 


THE  ASH  OF  PLAHTS.  193 

the  analyses  of  the  seeds  of  cereals,  ferric  oxide  ranges 
from  an  unweighable  trace  to  2  and  even  3%.  In  root 
crops  it  has  been  found  as  high  as  5%.  Kekule  found 
in  the  ash  of  gluten  from  wheat  7.1%  of  ferric  oxide. 
(Jahresbericht  der  Chem.,  1851,  p.  715.)  Schulz-Fleeth 
found  17.5%  in  the  ash  of  the  albumin  from  the  juice  of 
';he  potato  tuber.  The  proportion  of  ash  is,  however,  so 
small  that  in  case  of  potato-albumin  the  ferric  oxide 
amounts  to  but  0.12  per  cent  of  the  dry  substance.  (Der 
Rationelle  Ackerbau,  p.  82.) 

In  the  ash  of  v^ood,  and  especially  in  that  of  bark,  ferric 
oxide  often  exists  to  the  extent  of  5  to  10%.  The  largest 
percentages  have  been  found  in  aquatic  plants.  In  the 
ash  of  the  duckweed  (Lemna  trisulca)  Liebig  found 
7.4%.  Gorup-Besanez  found  in  the  ash  of  the  leaves  of 
the  Trapa  natans  29.6%,  and  in  the  ash  of  the  fruit- 
euvelope  of  the  same  plant  68.6%.  (Ann.  Ch.  Ph.,  118, 
p.  223.) 

Probably  much  of  the  iron  of  agricultural  and  land 
plants  is  accidental.  In  case  of  the  Trapa  natans,  we 
cannot  suppose  all  the  iron  to  be  essential,  because  the 
larger  share  of  it  exists  in  the  tissues  as  a  brown  powdery 
oxide  which  may  be  extracted  by  acids,  and  has  the  ap- 
pearance of  having  accumulated  there  mechanically. 

Doubtless  a  portion  of  the  iron  encountered  in  anal- 
yses of  agricultural  vegetation  has  never  once  existed 
within  the  vegetable  tissues,  but  comes  from  the  soil, 
which  adheres  with  great  tenacity  to  all  parts  of  plants. 

Manganese  is  Unessential  to  Agricultural  Plants. 
Manganese  is  commonly  much  less  abundant  than  iron, 
and  is  often,  if  not  usually,  as  good  as  wanting  in  agri- 
cultural plants.  It  generally  accompanies  iron  where 
the  latter  occurs  in  considerable  quantity.  Thus,  in  the 
ash  of  Trapa,  the  oxide  Mn304  was  found  to  the  extent 
of  7.5-14.7%.  Sometimes  it  is  found  in  much  larger 
quantity  than  oxide  of  iron  ;  e.  g.,  C.  Fresenius  found 
13 


194  HOW  CHOPS  GROW. 

11.2%  of  oxide  of  manganese  in  ash.  of  leaves  of  the  red 
beech  (Fagus  sylvaticd)  that  contained  but  1%  of  oxide 
of  iron.  In  the  ash  of  oak  leaves  (Quercus  robur)  Neu- 
bauer  found,  of  the  former  6.6,  of  the  latter  but  1.2%. 

In  ash  of  the  wood  of  the  larch  (Larix  Europcea],  Bot- 
tinger  found  13.5%  Mn304  and  4.2%  Fe203,  and  in  ash 
of  wood  of  Pinus  sylvestris  18.2%  Mu304,  and  3.5% 
Fe208.  In  ash  of  the  seed  of  colza,  Nitzsch  found  16.1% 
Mn304,  and  5.5  Fe203.  In  case  of  land  plants,  these 
high  percentages  are  accidental,  and  specimens  of  most 
of  the  plants  just  named  have  been  analyzed,  which  were 
free  from  all  but  traces  of  oxide  of  manganese. 

Salm-Horstmar  concluded  from  his  experiments  that 
oxide  of  manganese  is  indispensable  to  vegetation. 
Sachs,  Knop,  and  most  other  experimenters  in  water- 
culture,  make  no  mention  of  this  substance  in  the  mix- 
tures, which  in  their  hands  have  served  for  the  more  or 
less  perfect  development  of  a  variety  of  agricultural 
plants.  Birner  &  Lucanus  have  demonstrated  that  man- 
ganese is  not  needful  to  the  oat-plant,  and  cannot  take 
the  place  of  iron.  (  Vs.  St.,  VIII,  p.  43.) 

Is  Chlorine  Indispensable  to  Crops  ? — What  has 
been  written  of  the  occurrence  of  sodium  in  plants  ap- 
pears to  apply  in  most  respects  equally  well  to  chlorine. 
In  nature,  sodium  is  generally  associated  with  chlorine 
as  common  salt.  It  is  most  probably  in  this  form  that 
the  two  substances  usually  enter  the  plant,  and 'in  the 
majority  of  cases,  when  one  of  them  is  present  in  large 
quantity,  the  other  exists  in  corresponding  quantity. 
Less  commonly,  the  chlorine  of  plants  is  in  combination 
with  potassium  exclusively. 

Chlorine  is  doubtless  never  absent  from  the  perfect 
agricultural  plant,  as  produced  under  natural  conditions, 
though  its  quantity  is  liable  to  great  variation,  and  is 
often  very  small — so  small  as  to  be  overlooked,  except  by 
the  careful  analyst.  In  many  analyses  of  grain,  chlorine 


THE  ASH  OF  PLANTS.  195 

is  not  mentioned.  Its  absence,  in  many  cases,  is  due, 
without  doubt,  to  the  fact  that  chlorine  is  readily  dissi- 
pated from  the  ash  of  substances  rich  in  phosphates  or 
silica,  on  prolonged  exposure  to  a  high  temperature.  In 
some  of  the  later  analyses,  in  which  the  vegetable  sub- 
stance, instead  of  being  at  once  burned  to  ashes,  at  a 
high  red  heat,  is  first  charred  at  a  heat  of  low  redness, 
and  then  leached  with  water,  which  dissolves  the  chlo- 
rides, and  separates  them  from  the  unburned  carbon  and 
other  matters,  chlorine  is  invariably  mentioned.  In  the 
tables  of  analyses,  the  averages  of  chlorine  are  undeni- 
ably too  low.  This  is  especially  true  of  the  grains. 

The  average  of  chlorine  in  the  26  analyses  of  wheat  by 
"Way  and  Ogston,  p.  150,  is  but  0.08%,  it  not  being  found 
at  all  in  the  ash  of  21  samples.  In  Zoeller's  later  anal- 
yses chlorine  is  found  in  every  instance,  and  averages 
0.7%.  In  Lawes  and  Gilbert's  numerous  analyses  of 
wheat-grain  ash  chlorine  ranges  from  0  to  1.14%,  the 
average  being  0.1%.  In  wheat-straw  ash  they  found 
from  1.08  to  2.0G%.  The  ash  was  in  all  cases  prepared 
by  burning  at  a  low  red  heat. 

Like  sodium,  chlorine  is  particularly  abundant  in  the 
stems  and  leaves  of  those  kinds  of  vegetation  which  grow 
in  soils  or  other  media  containing  much  common  salt.  It 
accompanies  sodium  in  strand  and  marine  plants,  and,  in 
general,  the  content  of  chlorine  of  any  plant  may  be  large- 
ly increased  or  diminished  by  supplying  it  to  or  withhold- 
ing it  from  the  roots. 

As  to  the  indispensableness  of  chlorine,  we  have  some- 
what conflicting  data.  Salm-Horstmar  believed  that  a 
trace  of  it  is  needful  to  the  wheat  plant,  though  many  of 
his  experiments  in  reference  to  this  element  were  unsatis- 
factory to  himself.  Nobbe  and  Siegert,  who  have  made 
an  elaborate  investigation  on  the  nutritive  relations  of 
chlorine  to  buckwheat,  were  led  to  conclude  that  while 
the  stems  and  foliage  of  this  plant  are  able  to  attain  a 


196  HOW  CBOPS  GROW. 

considerable  development  in  the  absence  of  chlorine  (the 
miuute  amount  in  the  seed  itself  excepted),  presence  of 
chlorine  is  essential  to  the  perfection  of  the  fruit. 

Leydhecker  came  to  the  same  conclusions  as  Nobbe 
and  Siegert  regarding  the  indispensableness  of  chlorine 
to  the  perfection  of  buckwheat.  ( Vs.  St.,  VIII,  p.  177.) 

On  the  other  hand,  Knop  excludes  chlorine  from  the 
list  of  necessary  ingredients  of  maize,  buckwheat,  cress, 
and  Psamma  arenaria,  having  obtained  a  maize  plant  3 
feet  high,  bearing  4  ripe  seeds,  harvested  23  "  chlorine- 
free  seeds"  from  5  buckwheat-plants,  and  raised  40  to  50 
ripe  seeds  from  more  than  one  cress-plant,  all  grown 
without  chlorine.  (  Vs.  St.,  XIII,  p.  219.) 

Wagner  also  obtained,  in  absence  of  chlorine,  maize- 
plants  40  inches  high,  of  20  grams  dry-weight.  One  of 
these  ripened  5  small  seeds,  of  which  two  were  proved 
capable  of  germination ;  but  none  of  these  plants  produced 
any  pollen  and  they  were  fertilized  with  pollen  from 
garden-plants.  ( Vs.  St.,  XIII,  pp.  218-222.) 

From  a  series  of  experiments  in  water-culture,  Birner 
and  Lucanus  (Vs.  St.,  VIII,  p.  160)  conclude  that  chlo- 
rine is  not  indispensable  to  the  oat-plant,  and  has  no  spe- 
cific effect  on  the  production  of  its  fruit.  Chloride  of 
potassium  increased  the  weight  of  the  crop,  chloride  of 
sodium  gave  a  larger  development  of  foliage  and  stem, 
chloride  of  magnesium  was  positively  deleterious,  under 
the  conditions  of  their  trials. 

Lucanus  ( Vs.  St.,  VII,  pp.  363-71)  raised  clover  by 
water-culture  without  chlorine,  the  crop  (dry)  weigh- 
ing in  the  most  successful  experiments  240  times  as  much 
as  the  seed.  Addition  of  chlorine  gave  no  better  result. 

Nobbe  (Vs.  St.,  VIII,  p.  187)  has  produced  normally 
developed  vetch  and  pea  plants,  but  only  in  solutions 
containing  chlorine.  Beyer  (Vs.  St.,  XI,  p.  262)  found 
exclusion  of  chlorine  in  water-culture  to  prevent  forma- 
tion of  seed  in  case  of  peas ;  the  plants,  after  a  month's 


THE  ASfl  OP  PLANTS.  197 

healthy  growth,  produced  new  shoots  only  at  the  expense 
of  the  older  leaves.  In  similar  trials  oats  gave  a  small 
crop  of  ripe  seeds  when  chlorine  was  not  supplied. 
When,  however,  the  seeds  thus  obtained  nearly  free  from 
chlorine  were  vegetated  in  a  solution  destitute  of  this 
element  they  failed  to  produce  seed  again,  though  their 
growth  and  reproduction  were  normal  when  chlorine 
was  furnished  them  in  the  nutritive  solution. 

In  Plate  I,  X  shows  the  extent  to  which,  in  Nobbe's 
cultures,  buckwheat  developed  when  vegetating  for  3 
months  in  a  solution  destitute  of  chlorine,  but  otherwise 
fully  adapted  to  nourish  plants. 

In  view  of  all  the  evidence,  then,  it  would  appear 
probable  that  chlorine  is  needful  for  the  cereals,  and 
that  when  the  seed  and  nutritive  media  (soil  or  solution 
and  air)  are  entirely  destitute  of  this  element  fruit  cannot 
be  perfected.  It  is  probable  that  in  the  cases  where 
fruit  was  produced  in  supposed  absence  of  chlorine  this 
substance  in  some  way  gained  access  to  the  plants. 

Until  further  more  decisive  results  are  reached,  we 
are  warranted  in  adopting,  with  regard  to  chlorine  as 
related  to  agricultural  plants,  the  following  conclu- 
sions, viz. : 

1.  Chlorine  is  never  totally  absent. 

2.  If  indispensable,  but  a  minute  amount  is  requisite 
for  a  very  considerable  vegetative  development. 

3.  Some  plants,  as  vetches  and  peas,  require  a  not  in- 
considerable amount  of  chlorine  for  full  development, 
especially  of  seed. 

4.  The  foliage  and  succulent  parts  may  include  a 
large  quantity  of  chlorine  that  is  not  indispensable  to 
the  life  of  the  plant. 

Silica  is  not  indispensable  to  Plants. — The  numer- 
ous analyses  we  now  possess  indicate  that  this  substance 
is  always  present  in  the  ash  of  all  parts  of  agricultural 
plants,  when  they  grow  in  natural  soils. 


198  HOW  CROPS  GROW. 

In  the  ash  of  the  wood  of  trees,  it  usually  ranges  from 
1-3%,  but  is  often  found  to  the  extent  of  10-20%,  or 
even  30%,  especially  in  the  pine.  In  leaves,  it  is  usually 
more  abundant  than  in  stems.  The  ash  of  turnip  leaves 
contains  3-10%  ;  of  tobacco  leaves,  5-18%  ;  of  the  oat, 
11-58%.  (Arendt,  Norton.)  In  ash  of  lettuce,  20%  ;  of 
beech  leaves,  26%  ;  in  those  of  oak,  31%  have  been 
observed.  (Wicke,  Henneberg's  Jour.,  1862,  p.  156.) 

The  bark  or  cuticle  of  many  plants  contains  an  extra- 
ordinary amount  of  silica.  The  cauto  tree  of  South 
America  (Hirtella  silicza)  is  most  remarkable  in  this 
respect.  Its  bark  is  very  firm  and  harsh,  and  is  difficult 
to  cut,  having  the  texture  of  soft  sandstone.  It  yields 
34%  of  ash,  and  of  this  96%  is  silica.  (Wicke,  loc.  cit., 
p.  143.) 

Another  plant,  remarkable  for  its  content  of  silica,  is 
the  bamboo.  The  ash  of  the  rind  contains  70%,  and  in 
the  joints  of  the  stem  are  often  found  concretions  of 
hydrated  silica,  the  so-called  Tabashir. 

The  ash  of  the  common  scouring  rush  (Equisetum  hye~ 
male)  has  been  found  to  contain  97.5%  of  silica.  The 
straw  of  the  cereal  grains,  and  the  stems  and  leaves  of 
grasses,  both  belonging  to  the  botanical  family  Grami- 
nacce,  are  specially  characterized  by  a  large  content  of 
silica,  ranging  from  40-70%  of  the  ash.  The  sedge  and 
rush  families  likewise  contain  much  of  this  substance. 

The  position  of  silica  in  the  plant  would  thus  appear 
to  be,  in  general,  at  the  surface.  Although  it  is  present 
in  other  parts  of  the  plant,  yet  the  cuticle  is  usually  rich- 
est, especially  where  the  content  of  silica  is  large.  Davy, 
in  1799,  drew  attention  to  the  deposition  of  silica  in  the 
cuticle  of  the  grasses  and  cereals,  and  advanced  the  idea 
that  it  serves  these  plants  an  office  of  support  similar  to 
that  enacted  in  animals  by  the  bones. 

In  case  of  the  pine  (Pinus  sylvestris),  Wittstein  has 
obtained  results  which  indicate  that  the  age  of  wood  or 


THE  ASH  OF  PLANTS.  199 

bark  greatly  influences  the  content  of  silica.     He  found 
in  ash  of  the — 


And  in — 


Wood  of  a  tree,  220  years  old,  32.5% 
«  «  170          "          24.1 

«  «  135          "          15.1 


Bark          "  220          «          30.3 

"  "  170          «          14.4 

"  "  135          "          11.9 


In  the  ash  of  the  straw  of  the  oat,  Arendt  found  the 
percentage  of  silica  to  increase  as  the  plant  approached 
maturity.  So  the  leaves  of  forest  trees,  which  in  autumn 
are  rich  in  silica,  are  nearly  destitute  of  this  substance 
in  spring  time. 

Silica  accumulates  then,  in  general,  in  the  older  and 
less  active  parts  of  the  plant,  whether  these  be  external 
or  internal,  and  is  relatively  deficient  in  the  younger  and 
really  growing  portions.  This  rule  is  not  without  excep- 
tions. Thus,  the  chaff  of  wheat,  rye  and  oats  is  richer 
in  silica  than  any  other  part  of  these  plants,  and  Bottin- 
ger  found  the  seeds  of  the  pine  richer  in  silica  than  the 
wood. 

In  numerous  instances,  silica  is  deposited  in  or  upon 
the  cell-wall  in  such  abundance  that  when  the  organic 
matters  are  destroyed  by  burning,  or  removed  by  sol- 
vents, the  form  of  the  cell  is  preserved  in  a  silicious 
skeleton.  This  has  long  been  known  in  case  of  the 
Equisetums  and  Deutzias.  Here  the  peculiar  rough- 
nesses of  the  stems  or  leaves  are  fully  incrusted  or  inter- 
penetrated by  silica,  and  the  ashes  of  the  cuticle  present 
the  same  appearance  under  the  microscope  as  the  cuticle 
itself. 

The  hairs  of  nettles,  hemp,  hops,  and  other  rough- 
leaved  plants,  are  highly  silicious. 

According  to  Wicke,  the  beech  owes  the  smooth  and 
undecayed  surface  which  its  trunk  presents,  to  the  silica 
of  the  bark.  The  best  textile  materials,  which  are  bast- 


200  HOW  CROPS  GROW. 

fibers  of  various  plants,  viz.,  common  hemp,  Manila 
hemp  (Musa  textilis),  aloe-hemp  (Agave  Americana), 
common  flax,  and  New  Zealand  flax  (Phormium  tenax) 
are  incrusted  with  silica.  In  jute  (Corchorus  textilis) 
some  cells  are  partially  incrusted.  The  cotton  fiber  is 
free  from  silica.  Wicke  (loc.  cit.)  suggests  that  the  du- 
rability of  textile  fibers  is  to  a  degree  dependent  on  their 
content  of  silica. 

Sachs,  in  1862,  was  the  first  to  publish  evidence  that 
silica  is  not  a  necessary  ingredient  of  maize.  He  ob- 
tained in  his  early  essays  in  water-culture  a  maize  plant 
of  considerable  development,  whose  ashes  contained  but 
0.7%  of  silica.  Shortly  afterwards,  Knop  produced  a 
maize  plant  with  140  ripe  seeds,  and  a  dry-weight  of  50 
grammes  (nearly  2  oz.  av.)  so  free  from  silica  that  a 
mere  trace  of  this  substance  could  be  found  in  the  root, 
but  half  a  milligramme  in  the  stem,  and  22  milligrammes 
in  the  15  leaves  and  sheaths.  It  was  altogether  absent 
from  the  seeds.  The  ash  of  the  leaves  of  this  plant  thus 
contained  but  0. 54  per  cent  of  silica,  and  the  stem  but 
0.07  per  cent.  Way  &  Ogston  had  found  in  the  ash  of 
field-grown  maize,  leaf  and  stem  together,  27.98  per 
cent  of  silica. 

In  the  numerous  experiments  that  have  been  made 
more  recently  upon  the  growth  of  plants  in  aqueous  solu- 
tions, by  Sachs,  Knop,  Nobbe  &  Siegert,  Stohmann, 
Rautenberg  &  Kiihn,  Birner  &  Lucanus,  Leydhecker, 
Wolff,  and  Hampe,  silica,  in  nearly  all  cases,  has  been 
excluded,  so  far  as  it  is  possible  to  do  so,  in  the  use  of 
glass  vessels.  This  has  been  done  without  prejudice  to 
the  development  of  the  plants.  Nobbe  &  Siegert  and 
Wolff  especially  have  succeeded  in  producing  buckwheat, 
maize,  and  the  oat,  in  full  perfection  of  size  and  parts, 
with  this  exclusion  of  silica. 

Wolff  (  Vs.  St.,  VIII,  p.  200)  obtained  in  the  ash  of 
maize  thus  cultivated,  2  to  3%  of  silica,  while  the  same 


THE  ASH  OF  PLANTS.  201 

two  varieties  from  the  field  contained  in  their  ash  11£  to 
13%.  The  proportion  of  ash  was  essentially  the  same  in 
both  cases,  viz.,  about  6%.  Wolff's  results  with  the  oat 
plant  were  entirely  similar. 

Birner  &  Lucanus  (Vs.  St.,  VIII,  p.  141)  found  that 
the  supply  of  soluble  silicates  to  the  oat  made  its  ash  very 
rich  in  silica  (40%)  but  diminished  the  growth  of  straw, 
without  affecting  that  of  the  seed,  as  compared  with 
plants  nearly  destitute  of  silica. 

It  is  thus  made  certain  that  plants  ordinarily  rich  in 
silica  may  attain  a  high  development  in  absence  of  this 
substance.  We  shall  see  later,  however  (p.  ),  that 
silica  is  probably  not  altogether  useless  to  plants  when 
they  grow  under  ordinary  conditions. 

Jodin  reports  having  bred  maize  by  water-culture,  with 
ihe  utmost  practicable  exclusion  of  silica,  for  four  gener- 
ations— whereby  this  substance  was  reduced  to  the  merest 
traces — without  interference  with  the  normal  develop- 
ment of  the  plant.  (Ann.  Agron.,  IX,  p.  385.) 

The  Ash-Ingredients,  which  are  Indispensable 
to  Crops,  may  be  taken  up  in  Larger  Quantity  than 
is  Essential. — More  than  eighty  years  ago,  Saussure  de- 
scribed a  simple  experiment  which  is  conclusive  on  this 
point.  He  gathered  a  number  of  peppermint  plants,  and 
in  some  determined  the  amount  of  dry  matter,  which 
was  40.3  per  cent.  The  roots  of  others  were  then  im- 
mersed in  pure  water,  and  the  plants  were  allowed  to  veg- 
etate 2£  months  in  a  place  exposed  to  air  and  light,  but 
sheltered  from  rain. 

At  the  termination  of  the  experiment,  the  plants, 
which  originally  weighed  100,  had  increased  to  216  parts, 
and  the  dry  matter  of  these  plants,  which  at  first  was 
40.3,  had  become  62  parts.  The  plants  could  have 
acquired  from  the  glass  vessels  and  pure  water  no  con- 
siderable quantity  of  mineral  matters.  It  is  plain,  then, 
that  the  ash-ingredients  which  were  contained  in  two 


202  HOW  CROPS  GROW. 

parts  of  the  peppermint  were  sufficient  for  the  produc- 
tion and  existence  of  three  parts.  We  may  assume, 
therefore,  that  at  least  one-third  of  the  aeh  of  the  origi- 
nal plants  was  in  excess,  and  accidental. 

The  fact  of  excessive  absorption  of  essential  ash-ingre- 
dients is  also  demonstrated  by  the  precise  experiments  of 
Wolff  on  buckwheat,  already  described  (see  p.  164), 
where  the  point  in  question  is  incidentally  alluded  to, 
and  the  difficulties  of  deciding  how  much  excess  may 
occur,  are  brought  to  notice.  (See  also  pp.  192  and  194 
n  regard  to  potassium  and  iron.) 

As  further  striking  instances  of  the  influence  of  the 
nourishing  medium  on  the  quantity  of  ash-ingredients  in 
the  plant,  the  following  are  adduced,  which  may  serve  to 
put  in  still  stronger  light  the  fact  that  a  plant  does  not 
always  require  what  it  contains. 

Nobbe  &  Siegert  have  made  a  comparative  study  of 
the  composition  of  buckwheat,  grown  on  the  one  hand  in 
garden  soil,  and  on  the  other  in  an  aqueous  solution  of 
saline  matters.  (The  solution  contained  magnesium 
sulphate,  calcium  chloride,  phosphate  and  nitrate  of 
potassium,  witli  phosphate  of  iron,  which  together  con- 
stituted 0.316%  of  the  liquid.)  The  ash-percentage  was 
much  higher  in  the  water-plants  than  in  the  garden- 
plants,  as  shown  by  the  subjoined  figures.  ( Vs.  Si.,  V, 
p.  132.) 

Per  cent  of  ash  in 

Stems  and  leaves.       Hoots.          Seeds.  Entire  plant. 

Water-plant 18.6  15.3  2.6  16.7 

Garden-plant 8.7  6.8  2.4  7.1 

We  have  seen  that  well-developed  plants  contain  a 
larger  proportion  of  ash  than  feeble  ones,  when  they 
grow  side  by  side  in  the  same  medium.  In  disregard  of 
this  general  rule,  the  water-plant  in  the  present  instance 
has  an  ash-percentage  double  that  of  the  land-plant, 
although  the  former  was  a  dwarf  compared  with  the  lat- 
ter, yielding  but  £  as  much  dry  matter.  The  seeds,  how- 
ever, are  scarcely  different  in  composition. 


THE  ASH  OF  PLANTS.  203 

Similar  results  were  obtained  by  Councler  with  the 
leaves  of  Acer  negundo  (Vs.  St.,  XXIX,  p.  242),  1,000 
parts  of  the  perfectly  dry  leaves  contained  : 

Water-plant.  Soil-plant. 

Silica,  SiO2, 8.51  23.72 

SUphuri.;  oxide,  SO3, 38.97  9.69 

Phosphoric  oxide,  P2OB)... 26.00  4.56 

Iron  oxide,  Fe2O3, 1.94  1.22 

Magnesium  oxide,  MgO,. ..  7.56  6.25 

Calcium  oxide,  CaO, 31.77  36.17 

Sodium  oxide,  Na2O 1.23  0.88 

Potassium  oxide,  K2O, 96.92  45.05 

212.90  127.54 

Leaves  of  the  water-plant  are  much  richer  in  ash -ingre- 
dients, especially  in  sulphate  and  phosphate  of  potassium. 
Those  of  the  soil-plant  contain  more  silica  and  lime. 

Disposition  by  the  Plant  of  Excessive  or  Super- 
fluous Ash-ingredients — The  ash -ingredients  taken 
up  by  a  plant  in  excess  beyond  its  actual,  wants  may  be 
disposed  of  in  three  ways.  The  soluble  matters — those 
soluble  by  themselves,  and  also  incapable  of  forming  in- 
soluble combinations  with  other  ingredients  of  the  plant 
— viz.,  tbe  alkali  chlorides,  sulphates,  carbonates,  and 
phosphates,  the  chlorides  of  calcium  and  magnesium, 
may- 

1,  Remain  dissolved  in,  and  diffused  throughout,  the 
juices  of  the  plant ;  or, 

2.  May  exude  upon  the  surface  as  an  efflorescence,  and 
be  washed  off  by  rains. 

Exudation  to  the  surface  has  been  repeatedly  observed 
in  case  of  cucumbers  and  other  kitchen  vegetables,  grow- 
ing in  the  garden,  as  well  as  with  buckwheat  and  barley 
in  water-culture.  (  Vs.  St.,  VI,  p.  37.) 

Saussure  found  in  the  white  incrustations  upon  cucum- 
ber leaves,  besides  an  organic  body  insoluble  in  water  and 
alcohol,  calcium  chloride  with  a  trace  of  magnesium 
chloride.  The  organic  substance  so  enveloped  the  cal- 
cium chloride  as  to  prevent  deliquescence  of  the  latter. 
(Recherches  sur  la  Veg.t  p.  265.) 


204  HOW  CHOPS  GROW. 

Saussure  proved  that  foliage  readily  yields  up  saline 
matters  to  water.  He  placed  hazel  leaves  eight  success- 
ive times  in  renewed  portions  of  pure  water,  leaving  them 
therein  15  minutes  each  time,  and  found  that  by  this 
treatment  they  lost  -^  of  their  ash-ingredients.  The 
portion  thus  dissolved  was  chiefly  alkaline  salts  ;  but  con- 
sisted in  part  of  earthy  phosphates,  silica,  and  oxide  of 
iron.  (Recherches,  p.  287.) 

Bitthausen  has  shown  that  clover  which  lies  exposed  to 
rain  after  being  cut  may  lose  by  washing  more  than  one- 
half  of  its  ash-ingredients. 

Mulder  (Chemie  der  Ackerkrume,  II,  p.  305)  attributes 
to  loss  by  rain  a  considerable  share  of  the  variations  in 
percentage  and  composition  of  the  fixed  ingredients  of 
plants.  We  must  not,  however,  forget  that  all  the  exper- 
iments which  indicate  great  loss  in  this  way  have  been 
made  on  the  cut  plant,  and  their  results  may  not  hold 
good  to  the  same  extent  for  uninjured  vegetation. 

3.  The  insoluble  matters,  or  those  which  become  so  in 
the  plant,  viz.,  the  calcium  sulphate,  the  oxalates,  phos- 
phates, and  carbonates  of  calcium  and  magnesium,  the 
oxides  of  iron  and  manganese,  and  silica,  may  be  depos- 
ited as  crystals  or  concretions  in  the  cells,  or  may  incrust 
the  cell- walls,  and  thus  be  set  aside  from  the  sphere  of 
vital  action. 

In  the  denser  and  comparatively  juiceless  tissues,  as  in 
bark,  old  wood,  and  ripe  seeds,  we  find  little  variation  in 
the  amount  of  soluble  matters.  These  are  present  in 
large  and  variable  quantity  only  in  the  succulent  organs. 

In  bark  (cuticle),  wood,  and  seed  envelopes  (husks, 
shells,  chaff)  we  often  find  silica,  the  oxides  of  iron 
and  manganese,  and  calcium  carbonate — all  insoluble 
substances — accumulated  in  considerable  amount.  In 
bran,  phosphate  of  magnesium  exists  in  comparatively 
large  quantity.  In  the  dense  teak  wood,  concretions  of 
calcium  phosphate  have  been  noticed.  Of  a  certain 


THE  ASH  OF  PLANTS.  205 

species  of  cactus  (Cactus  senilis)  80%  of  the  dry 
matter  consists  of  crystals  of  calcium  oxalate  and  phos- 
phate. 

That  the  quantity  of  matters  thus  segregated  is  in  some 
degree  proportionate  to  the  excess  of  them  in  the  nourish- 
ing medium  in  which  the  plant  grows  has  been  observed 
by  Nobbe  &  Siegert,  who  remark  that  the  two  portions 
of  buckwheat,  cultivated  by  them  in  solutions  and  in  gar- 
den-soil respectively  (p.  203),  both  contained  crystals 
and  globular  crystalline  masses,  consisting  probably  of 
calcium  and  magnesium  oxalates,  and  phosphates,  depos- 
ited in  the  rind  and  pith  ;  but  that  these  were  by  far  most 
abundant  in  the  water-plants  whose  ash-percentage  was 
twice  as  great  as  that  of  the  garden-plants. 

These  insoluble  substances  may  be  either  entirely  unes- 
sential, or,  having  once  served  the  wants  of  the  plant,  may 
be  rejected  as  no  longer  useful,  and  by  assuming  the  in- 
soluble form,  are  removed  from  the  sphere  of  vital  action, 
and  become  in  reality  dead  matter.  They  are,  in  fact, 
excreted,  though  not,  in  general, 
formally  expelled  beyond  the  limits 
of  the  plant.  They  are,  to  some 
extent,  thrown  off  into  the  bark 
or  into  the  older  wood  or  pith, 
or  else  are  encysted  in  the  living 
cells. 

The  occurrence  of  crystallized  salts 
thus  segregated  in  the  cells  of  plants 
is  illustrated  by  the  following  cuts. 
Fig.  23  represents  a  crystallized  con- 
cretion of  calcium  oxalate,  having  a  basis  or  skeleton  of 
cellulose,  from  a  leaf  of  the  walnut.  (Payen,  Chimie  In- 
dustrielle,  PL  XII. )  Fig.  24  shows  a  mass  of  crystals  of  the 
same  salt,  from  the  leaf  stem  of  rhubarb.  Fig.  25  illus- 
trates similar  crystals,  from  the  beet  root.  In  the  root  of 
the  young  bean,  Sachs  found  a  ring  of  cells,  containing 


206 


HOW  CROPS  GROW. 


crystals  of  sulphate  of  lime.     (Sitzungsberichte  der  Wien. 
Akad.,  37,  p.  106.)     Bailey  ob- 
served in  certain  parts  of  the  in- 
ner bark  of  the  locust  a  series  of 
cells,  each  of  which  contained  a 
crystal.     In  the  onion-bulb,  and 
many  other  plants,   crystals  are 
Fig'25'       abundant.      (Gray's    Botanical 
Text-Book,  6th  ed.,  Vol.  II,  p.  52.) 

Instances  are  not  wanting  in  which  there  is  an  obvious 
excretion  of  mineral  matters,  or  at  least  a  throwing  of 
them  off  to  the  surface.  Silica,  as  we  have  seen,  is  often 
found  in  the  cuticle,  but  is  usually  imbedded  in  the  cell- 
wall.  In  certain  plants,  other  substances  accumulate  in 
considerable  quantity  without  the  cuticle.  A  striking  ex- 
ample is  furnished  by  Saxifraga  crustata,  a  low  European 
plant,  which  is  found  in  lime  soils. 
The  leaves  of  this  saxifrage  are  en- 
tirely coated  with  a  scaly  incrusta 
tion  of  calcium  and  magnesium 
carbonates.  At  the  edges  of  the 
leaf  this  incrustation  acquires  a 
considerable  thickness,  as  is  illus- 
trated by  figure  26,  a.  In  an  anal- 
ysis made  by  linger,  to  whom  these 
facts  are  due,  the  fresh  (undried) 
leaves  yielded  to  a  dilute  acid 
4.14%  of  calcium  carbonate,  and 
0.82%  of  magnesium  carbonate. 

linger  learned  by  microscopic 
investigation  that  this  excretion 
of  carbonates  proceeds  mostly  from  a  series  or  granular 
expansions  at  the  margin  of  the  leaf,  which  are  directly 
connected  with  the  sap-ducts  of  the  plant.  (Sitzungsbe- 
richte  der  Wien.  Akad.,  43,  p.  519.) 

Iu  figure  26,  a  represents  the  appearance  of  a  leaf,  magnified  4J  diam- 


')   «® 


</' 

Fig.  26. 


THE  ASH  OF  PLANTS.  20? 

feters.  Around  the  borders  are  seen  the  scales  of  carbonates ;  some  of 
these  have  been  detached,  leaving  round  pits  on  the  surface  of  the  leaf : 
c,  d  exhibit  the  scales  themselves,  e  in  profile :  b  shows  a  leaf,  freed 
from  its  incrustation  by  an  acid,  and  from  its  cuticle  by  potash-solution, 
so  as  to  exhibit  the  veins  (ducts)  and  glands,  whose  course  the  carbon- 
ates chiefly  take,  in  their  passage  through  the  plant. 

Further  as  to  the  state  of  ash-ingredients — It  iff 
by  no  means  true  that  the  ash-ingredients  always  exist  in 
plants  in  the  forms  under  which  they  are  otherwise  famil- 
iar to  us. 

Arendt  and  Hellriegel  have  studied  the  proportions  of 
soluble  and  insoluble  matters,  the  former  in  the  ripe  oat 
plant,  and  the  latter  in  clover  at  various  stages  of  growth. 

Arendt  extracted  from  the  leaves  and  stems  of  the  oat 
plant,  after  thorough  grinding,  the  whole  of  the  soluble 
matters  by  repeated  washings  in  water.*  He  found  that 
all  the  sulphuric  acid  and  all  the  chlorine  were  soluble. 
Nearly  all  the  phosphoric  acid  was  removed  by  water. 
The  larger  share  of  the  calcium,  magnesium,  sodium  and 
potassium  compounds  was  soluble,  though  portions  of  each 
escaped  solution.  Iron  was  found  in  both  the  soluble  and 
insoluble  state.  In  the  leaves,  iron  was  found  among  the 
insoluble  matters  after  all  phosphoric  acid  had  been  re- 
moved. Finally,  silica  was  mostly  insoluble,  though  in 
all  cases  a  small  quantity  occurred  in  the  soluble  condi- 
tion, viz.,  3-8  parts  in  10,000  of  the  dry  plant.  (Wach- 
sthum  der  Haferpflanze,  pp.  168,  183-4.  See,  also,  table 
on  p.  171). 

Weiss  and  Wiesner  discovered  by  microchemical  in- 
vestigation that  iron  exists  as  insoluble  ferrous  and  ferric 
compounds  both  in  the  cell-membrane  and  in  the  cell- 
contents.  (Sitzungsberichte  der  Wiener  Akad.,  40,  278.) 

Hellriegel  found  that  in  young  clover  a  larger  propor- 
tion of  the  various  bases  was  soluble  than  in  the  mature 
plant.  As  a  rule,  the  leaves  gave  most  soluble  matters, 
the  leaf  stalks  less,  and  the  stems  least.  He  obtained, 

*To  extract  the  soluble  parts  of  the  grain  in  this  way  was  impossible, 


208  HOW  CEOPS  GROW. 

among  others,  the    following    results    (Vs.    St.,    IV, 
p.  59)  : 

Of  100  parts  of  the  following  fixed  ingredients  of  clover, 
were  dissolved  in  the  sap,  and  not  dissolved — 


In  young  leaves.   In  full-grown  leaves. 
( dissolved . . . 
• '  ( undissolved 

Lime. 


Pntn«h  (dissolved ...75.2  37.3 

rotasn <  undissolved 24.8  62.7 


(dissolved 69.5  72.4 

(undissolved 30.5  27.6 

Ma«TnP«ia         (dissolved 43.6  78.3 

Magnesia . . .  J  undissolved 50.4  21.7 

Phosphoric    (dissolved 20.9  19.9 

oxide,  P»O5  \  undissolved 79.1  80.1 

«««„<,  (dissolved 26-8  16.1 

ca I  undissolved 73.2  83.9 

These  researches  demonstrate  that  potassium  and  sodi- 
um— bodies,  all  of  whose  commonly-occurring  compounds, 
silicates  excepted,  are  readily  soluble  in  water — enter  into 
insoluble  combinations  in  the  plant ;  while  phosphoric 
acid,  which  forms  insoluble  salts  with  calcium,  magnesi- 
um, and  iron,  is  freely  soluble  in  connection  with  these 
bases  in  the  sap. 

It  should  be  added  that  sulphates  may  be  absent  from 
the  plant  or  some  parts  of  it,  although  they  are  found  in 
the  ashes.  Thus,  Arendt  discovered  no  sulphates  in  the 
lower  joints  of  the  stem  of  oats  after  blossom,  though  in 
the  upper  leaves,  at  the  same  period,  sulphuric  oxide 
(S03)  formed  nearly  7%  of  the  sum  of  the  fixed  ingre- 
dients. (Wachsthum  der  Haferpf.,  p.  157.)  Ulbricht 
found  that  sulphates  were  totally  absent  from  the  lower 
leaves  and  stems  of  red  clover,  at  a  time  when  they  were 
present  in  the  upper  leaves  and  blossom.  ( Vs.  St.,  IV. ,  p. 
30  Tabelle. )  Both  Arendt  and  Ulbricht  observed  that  sul- 
phur existed  in  all  parts  of  the  plants  they  experimented 
upon  ;  in  the  parts  just  specified,  it  was,  however,  no 
longer  combined  to  oxygen,  but  had,  doubtless,  become 
an  integral  part  of  some  albuminoid  or  other  complex  or- 
ganic body.  Thus  the  oat  stem,  at  the  period  above  cited, 
contained  a  quantity  of  sulphur,  which,  had  it  been  con- 
verted into  sulphuric  oxide,  would  have  amounted  to 


THE  ASH  OF  PLANTS.  209 

of  the  fixed  ingredients.  In  the  clover  leaf,  at  a  time 
when  it  was  totally  destitute  of  sulphates,  there  existed 
an  amount  of  sulphur  which,  in  the  form  of  sulphuric 
oxide,  would  have  made  13.7%  of  the  fixed  ingredients, 
or  one  per  cent  of  the  dry  leaf  itself.* 

Other  ash-ingredients.— Salm-Horstmar  has  describ- 
ed some  experiments,  from  which  he  infers  that  a  minute 
amount  of  Lithium  and  Fluorine  (the  latter  as  fluoride 
of  potassium)  are  indispensable  to  the  fruiting  of  barley. 
(Jour,  fur prakt.  Chem.,  84.  p.  140.)  The  same  observer, 
some  years  ago,  was  led  to  conclude  that  a  trace  of  Titan- 
ium is  a  necessary  ingredient  of  plants.  The  later  re- 
sults of  water-culture  would  appear  to  demonstrate  that 
these  conclusions  are  erroneous. 

The  rare  alkali-metal,  Rubidium,  has  been  found  in  the 
sugar-beet,  in  tobacco,  coffee,  tea,  and  the  grape.  It  doubt- 
less occurs,  perhaps  together  with  the  similar  Caesium  in 
many  other  plants,  though  always  in  very  minute  quan- 
tity. Birner  and  Lucanus  found  that  these  bodies,  in  the 
absence  of  potassium,  acted  as  poisons  to  the  oat.  (  Vs. 
St.,  VIII,  p.  147.) 

According  to  Nobbe,  Schroeder  and  Erdmann,  Lith- 
ium is  very  injurious  to  buckwheat,  even  in  presence  of 
potassium.  When  lithium  was  substituted  for  two- 
thirds  of  the  potassium  of  a  normal  nutritive  solution, 
buckwheat  vegetated  indeed  for  3  months,  the  stem 
reaching  a  length  of  18  inches,  but  the  plant  was  small 
and  unhealthy,  the  leaves  were  pale  and  the  older  ones 
dropped  away,  as  shown  by  VIII,  plate  I.  (Vs.  St., 
XIII,  p.  356). 

*Arendtvrns  the  first  to  estimate  sulphuric  oxide  (SO3)  in  vegetable 
matters  with  accuracy,  and  to  discriminate  it  from  the  sulphur  of  or- 
ganic compounds.  This  chemist  separated  the  sulphates  of  the  oat- 
plant  by  extracting  the  pulverized  material  with  acidulated  water.  He 
likewise  estimated  the  total  sulphur  by  a  special  method,  and  by  sub- 
tracting the  sulphur  of  the  sulphuric  oxide  from  the  total  he  obtained  as 
a  difference  that  portion  of  sulphur  which  belonged  to  the  albuminoids, 
etc.  In  his  analysis  of  clover,  t'/hrifltt  followed  a  similar  plan.  ( frs.  St., 
Ill,  p.  147.)  As  has  already  been  stated,  many  of  the  older  analyses  are 
Wholly  untrustworthy  as  regards  sulphur  anil  sulphuric  oxide. 


810  HOW  CROPS  GROW. 

The  investigations  of  A.  Braun  and  of  Risse  (Sachs, 
Exp.  Physiologic,  153)  show  that  Zinc  is  a  usual  ingredi- 
ent of  plants  growing  about  zinc-mines,  where  the  soil 
contains  carbonate  or  silicate  of  this  metal.  Certain 
marked  varieties  of  plants  are  peculiar  to,  and  appear  to 
have  been  produced  by,  such  soils,  viz.,  a  violet  ( Viola 
tricolor,  var.  calaminaris),  and  a  shepherd's  purse 
(Thlaspi  alpestre,  var.  calaminaris).  In  the  ash  of  the 
leaves  of  the  latter  plant,  Eisse  found  13%  of  oxide  of 
zinc  ;  in  other  plants  he  found  from  0.3  to  3.3%.  These 
plants,  however,  grow  equally  well  in  absence  of  zinc, 
which  may  slightly  modify  their  appearance,  but  is  unes- 
sential to  their  nutrition. 

Boron  as  boric  acid  has  recently  been  found  in  many 
wines  of  California  and  Europe. 

Copper  is  often  or  commonly  found  in  the  ashes  of 
plants ;  and  other  elements,  viz.,  Arsenic,  Barium  and 
Lead,  have  been  discovered  therein,  but  as  yet  we  are  not 
warranted  in  assuming  that  any  of  these  substances  are 
of  importance  to  agricultural  vegetation.  The  soluble 
compounds  of  copper,  arsenic  and  lead  are  in  fact  very 
injurious  to  plant  life,  unless  very  highly  diluted. 

Iodine,  an  invariable  and  probably  a  necessary  constit- 
uent of  many  algae,  is  not  known  to  exist  to  any  consid- 
erable extent  or  to  be  essential  in  any  cultivated  plants. 

§4. 

FUNCTIONS    OP   THE    ASH-INGREDIENTS. 

Although  much  has  been  written,  little  is  certainly 
known,  with  reference  to  the  subject  of  this  section. 

Sulphates. — The  albuminoids,  which  contain  sulphur 
as  an  essential  ingredient,  obviously  cannot  be  produced 
in  absence  of  sulphates,  which,  so  far  as  we  know,  are  the 
exclusive  source  of  sulphur  to  plants.  The  sulphurized 


THE  ASH  OF  PLANTS.  211 

oils  of  the  onion,  mustard,  horse-radish,  turnip,  etc.,  like- 
wise require  sulphates  for  their  organization. 

Phosphates. — The  phosphorized  substances  (prota- 
gon,  lecithin,  chlorophyl}  require  to  their  elaboration  that 
phosphates  be  at  the  disposal  of  the  plant.  Knop  has  shown 
that  hypophosphites  cannot  take  the  place  of  phosphates. 
The  albuminoids  which  are  probably  formed  in  the  foliage 
must  pass  thence  through  the  cells  and  ducts  of  the  stem 
into  growing  parts  of  the  plant,  and  into  the  seed,  where 
they  accumulate  in  large  quantity.  But  the  albuminoids 
penetrate  membranes  with  great  difficulty  and  slowness 
when  in  the  pure  state.  The  di-  and  tri-potassic  phosphates 
dissolve  or  form  water-soluble  compounds  with  many 
albuminoids,  and,  according  to  Schumacher  (Physik  der 
Pflanze,  p.  128),  considerably  increase  the  diffusive  rate 
of  these  bodies,  and  thus  facilitate  their  translocation  in 
the  plant. 

Potassium. — The  organic  acids,  viz.,  oxalic,  malic, 
tartaric,  citric,  etc.,  require  potassium  to  form  the  salts 
of  this  metal,  which  exist  abundantly  in  plants,  e.  g., 
potassium  oxalate  in  sorrel,  potassium  bitartrate  in  the 
grape,  potassium  malate  in  garden  rhubarb  ;  and  without 
potassium  it  is  in  most  cases  probably  impossible  for  the 
acids  to  accumulate  or  to  be  formed.  Mercadante  culti- 
vated sorrel  (Oxalis  acetosella  and  Rumex  acetosa),  in  ab- 
sence of  potassium-salts;  sodium,  calcium,  and  magnesium 
being  supplied.  The  plants  failed  to  fructify,  and  their 
juices  contained  but  one-eighth  as  much  free  acid  (or  acid 
salts?)  as  exists  in  the  sap  of  the  same  kind  of  plants  veg- 
etating under  normal  conditions.  The  acids — oxalic,  with 
a  little  tartaric — were  united  to  calcium  (Berichte,  1875, 
II,  p.  1200).  The  organic  acids  may  result  from  the  de- 
composition of  carbhydrates  (starch  or  sugar),  or  they 
may  be  preliminary  stages  in  the  production  of  the  carb- 
hydrates. In  either  case  their  formation  is  an  index  to 
the  constructive  processes  by  which  the  plant  originates 


212  HOW  CROPS  GROW. 

new  vegetable  substance  and  increases  in  dry  weight. 
Alercad  ante's  observations  are  therefore  in  accord  with  the 
results  of  the  investigations  next  to  be  considered. 

In  1869,  Nobbe,  Schroder,  and  Erdmann  employed  the 
method  of  water-culture  to  make  an  elaborate  study  of 
the  influence  of  potassium  on  the  vegetative  processes, 
and  found  that,  all  other  needful  conditions  of  growth 
being  supplied,  in  absence  of  potassium  buckwheat 
plants  vegetated  for  three  months  without  any  increase  in 
weight — that  is  to  say,  without  producing  new  vegetable 
matter.  Examination  of  these  miniature  plants  demon- 
strated that  (in  absence  of  potassium)  the  first  evident 
stage  in  the  production  of  vegetable  substance,  viz.,  the 
appearance  of  starch  in  the  chlorophyl  granules  of  the 
leaf,  could  not  be  attained.  The  experimenters  therefore 
drew  the  conclusion  that  potassium  is  an  essential  factor 
in  the  assimilation  of  carbon  and  the  formation  of  starch. 
They  found  that  the  plants  were  able  to  produce  starch 
when  potassium  was  supplied  either  as -chloride,  nitrate, 
phosphate  or  sulphate.  The  transfer  of  the  starch  from 
the  leaves  to  the  fruit,  or  its  conversion  into  a  soluble 
form,  appeared  to  require  the  presence  of  chlorine  ;  ac- 
cordingly, potassium  chloride  gave  the  best  developed 
plants,  especially  at  the  period  of  fructification.  This 
conclusion  was  greatly  strengthened  by  the  observation, 
repeatedly  made,  that  the  miniature  plants  which  had 
vegetated  for  three  or  four  weeks  without  increase  of 
weight,  or  growth  other  than  that  which  the  seedling  can 
make  at  the  expense  of  the  seed,  began  at  once,  on  suit- 
able addition  of  potassium  chloride  to  the  nutritive  solu- 
tion, to  form  starch,  discoverable  in  all  the  chlorophyl 
granules,  and  thenceforward  developed  new  stems  and 
leaves  and  grew  in  quite  the  normal  manner.  In  Plate 
I  the  appearance  of  some  of  the  plants  produced  in  these 
trials  is  shown.  la  represents  the  average  plant  raised 
in  the  normal  solution  containing  abundance  of  potas- 


PLATE  I. 

KXri.ANATIoV.      (See  p.  2I2.) 

Water-cultures  of  Japanese  Buckwheat,  supplied  with  the  irjfcre- 
, Ii<-iiis  of  ;i  \iiriintf  Solution,  vi/. :  Sulphates,  Nitrates,  Phosphates  and 
chlorides  of  1'otassi inn,  Magnesium,  Calcium  and  Iron,  except  as  stated 
below. 

I  and  la.    Solution  normal.    Potassium  as  Chloride. 

II.  Solution  without  Potassium. 

ll:i.  Without  Potassium  for  4  weeks,  thereafter  Potassium  Chloride. 

III.  Potassium  as  Nitrate.    Chlorine  as  in  Normal. 

IV.  Potassium  as  Sulphate.    Chlorine  one-fourth  of  Normal. 

V.  Potassium  as  Phosphate.    Chlorine  one-tilth  ol  Normal. 

VI.  Sodium  but  not  Potassium. 

VIII.  Lithium. 

IX.  Without  Caleinm. 

X.  Without  Chlorine. 

XI.  Without  Nitrogen. 

The  meter-scale  (,3'Jj*  inches)  serves  to  measure  the  dimensions  of  the 
plants. 


KXIM.AXATIOX.     (See  p.  213.) 

Water-cultures  of  Flowering  Bean  after  vegetating  38  days. 

a.  In  normal  solution,  seed  Avith  cotyledons. 

b.  In  normal  solution,  seed  without  cotyledons. 

c.  In  potassium-free  solution,  seed  with  cotyledons. 

d.  In  potassium-free  solution,  seed  without  cotyledons. 


THE  ASH  OP  PLAHTS.  213 

slum  chloride.  II  was  deprived  of  potassium  save  that 
contained  in  the  seed.  In  IV  and  V,  respectively,  the 
chlorine  of  the  solution  was  reduced  to  one-fourth  and 
one-fifth  the  amounts  contained  in  the  normal  solution 
and  replaced  by  sulphuric  acid  in  IV  and  by  phosphoric 
acid  in  V.  In  case  of  II8,  the  plant  vegetated  without 
potassium  for  four  weeks  with  a  result  similar  to  II,  and 
then  for  two  months  was  supplied  with  potassium  chlo- 
ride. For  numerous  interesting  details  reference  must 
be  made  to  the  original  paper  (Vs.  8t.,  XIII,  pp. 
321-424). 

Lupke,  from  water-cultures  with  the  flowering  bean 
Phaseolus  multiflorus,  and  common  bean  P.  vulgaris, 
has  recently  arrived  at  different  conclusions.  He  finds 
that  these  plants  are  able,  under  the  utmost  possible  ex- 
clusion of  potassium,  to  assimilate  carbon  and  produce 
starch,  in  fact  to  grow  and  to  carry  on  all  the  vegetative 
functions  that  belong  to  the  fully-nourished  plant, 
though  on  a  diminished  scale.  In  order  to  limit  the 
supply  of  potassium  to  the  utmost,  the  cotyledons  of  some 
of  the  plants  were  cut  away  when  the  plumule  began  to 
appear  above  them.  In  this  way  90%  of  the  potassium 
of  the  seed  was  removed*  and  while  the  plants  were 
thereby  reduced  in  dimensions,  their  power  to  vegetate 
in  a  healthy  manner  was  not  suppressed.  After  65  days 
of  vegetation  one  of  these  plants  yielded  a  crop  of  dry- 
substance  4.8  times  as  much  as  was  contained  in  the 
newly  sprouted  seedling  after  excision  of  the  cotyledons. 

Some  results  of  these  cultures  are  shown  in  Plate  II. 
The  stem  of  the  unmutilated  flowering  bean  in  normal 
solution  I,  a,  reached  a  final  length  of  80  inches,  that  de- 
prived of  potassium  grew  to  40  inches. 

Nobbe's  conclusion  that  potassium  is  specifically  essen- 
tial or  concerned  in  starch-production  is  accordingly  erro- 

*  Lupke  found  that  one  seed  of  P.  multiflorus  contained  23  milligrams 
of  potassium  oxide;  the  seedling,  after  cutting  off  the  cotyledons,  con- 
tains 2.3  mm. 


214  HOW  CROPS  GROW. 

neous.  As  Lupke  remarks,  potassium  is  rather  like  nitro- 
gen, phosphorus,  sulphur,  etc.,  one  of  the  elements  of 
which  probably  a  certain  quantity  is  indispensable  to  the 
formation  of  every  vegetable  cell.  Nobbe's  results  per- 
haps indicate  that  buckwheat  requires  relatively  more 
potassium  than  the  bean  for  its  processes  of  growth. 
(Land.  MrMcJier,  1888,  pp.  887-913.) 

Calcium. — Bohm  (Jahresbericht  tiber  Ag.  Chemie, 
1875-6,  Bd.  I,  p.  255)  and  Von  Raumer  (  Vs.  St.,  XXIX, 
251)  have  furnished  evidence  that  calcium  (lime)  is  di- 
rectly necessary  to  the  formation  of  cell-tissue,  that  is  to 
say,  of  cellulose. 

This  evidence  rests  upon  observations  made  with  seed- 
lings of  the  flowering  bean  (scarlet-runner),  Phaseolus 
multiflorus.  When  a  seed  sprouts,  the  young  plant  at  first 
is  nourished  exclusively  by  the  nutritive  matters  contained 
in  the  seed.  When  its  roots  enter  the  soil  it  begins  to  de- 
rive water,  nitrogen,  and  ash-ingredients  from  the  earth. 
When  its  leaves  unfold  in  the  light  it  begins  to  gather 
carbon  from  the  air  and  to  increase  in  weight.  If  its 
roots  are  placed  in  pure  water  it  can  acquire  no  ash-in- 
gredients ;  if  its  leaves  are  kept  in  darkness  it  can  gain 
nothing  from  the  air.  Thus  circumstanced,  it  may  live 
and  vegetate  for  a  time,  but  constantly  loses  in  total  dry 
weight,  and  its  apparent  growth  is  only  the  formation  of 
new  parts  at  the  expense  of  the  old.  For  some  days  the 
young  stem  shoots  upward  without  green  color,  but  per- 
fectly formed,  and  then  (in  case  of  the  flowering  bean) 
euddenly,  at  a  little  space  below  the  terminal  bud,  a  dis- 
coloration appears,  the  stem  wilts,  withers,  and  dies 
away.  The  growth  of  stem  that  thus  occurs  is  accom- 
panied by  and  depends  upon  the  solution  of  starch  in  the 
seed-lobes  and  its  transfer  to  the  points  of  growth  where 
it  is  made  over  into  cellulose — the  frame-work  of  the 
stem.  In  absence  of  any  external  source  of  ash-ingredi- 
ents the  young  stem  dies  long  before  the  starch  of  the 


THE  ASH  OF  PLANTS.  215 

cotyledons  is  consumed.  But  if  the  roots  be  placed  in 
a  nutritive  solution  suited  to  water-culture,  the  stem 
grows  on  without  injury  until  the  cotyledons  are  com- 
pletely emptied  of  starch,  and  afterwards  continues  to  de- 
velop at  the  expense  of  the  lower  leaves. 

The  arrest  of  growth  in  the  stem  evidently  is  due  to 
the  absence  of  some  one  or  more  ash-ingredients,  and 
Bohm  found  in  fact  that,  by  withholding  lime-salts  from 
the  roots,  this  characteristic  malady  was  invariably  pro- 
duced. Hence  he  concludes  that  calcium  compounds  are 
immediately  concerned  in  the  conversion  of  starch  into 
cellulose. 

Magnesium.— Von  Eaumer,in  the  paper  just  referred 
to  ( Vs.  St.,  XXIX,  pp.  263  and  273),  gives  his  observa- 
tions on  the  relations  of  the  magnesium  salts  to  the  veg- 
etative processes.  He  states  that,  all  other  conditions 
being  favorable,  the  exclusion  of  magnesium  from  a  nu- 
tritive solution  in  which  the  scarlet-runner  vegetates  is 
followed  by  cessation  of  chlorophyl-production  and  of 
that  enlargement  of  the  new-formed  cells  wherein  the 
act  of  growth  largely  consists.  Accordingly,  in  absence 
of  magnesium-supply,  the  plants,  which  at  first  grew  nor- 
mally, after  reaching  a  height  of  forty  inches,  began  to 
show  signs  of  disturbed  nutrition.  The  uppermost  in- 
ternodes  (joints)  of  the  stems  almost  ceased  to  lengthen 
and  became  exceptionally  thick  and  hard,  their  leaves 
failed  to  open,  and  both  joints  and  leaves  were  white  in 
color  with  but  the  faintest  tint  of  green.  Soon  new  up- 
ward growth  ceased  altogether,  the  terminal  bud  and 
unfolded  leaves  dried  away,  and,  while  the  lower,  first- 
formed  and  green  leaves  remained  fresh  for  weeks  and 
the  lower  stem  threw  out  new  shoots,  healthy  growth 
was  at  a  stand-still,  and  the  plants  gradually  withered 
and  perished.  The  normal  growth  of  the  bean  plants 
for  a  month  or  more  in  nutritive  solutions  containing  no 
magnesium  is  accounted  for  by  the  supply  of  this  ele- 


216  SOW  CROPS  GROW. 

ment  existing  in  the  seed,*  which  evidently  was  enough 
for  the  necessities  of  growth  until  the  stem  was  forty 
inches  high.  From  that  point  on  the  plants  almost 
ceased  to  grow,  and  gradually  died  from  want  of  food 
and  inability  to  assimilate. 

We  have  already  seen  that,  according  to  Hoppe-Seyler, 
magnesium  is  a  constant  and  presumably  an  essential  in- 
gredient of  chlorophyllan,  a  crystallized  derivative  of 
chlorophyl.  This  makes  evident  that  magnesium  is  di- 
rectly concerned  in  and  needful  to  the  formation  of  the 
chlorophyl  granules  which,  so  far  as  observation  as  yet 
has  gone,  are  the  seat  of  those  operations  which  first 
construct  organic  substance  from  inorganic  matter. 

Magnesium  and  calcium  occur  in  the  aleurone  of  seeds 
and,  according  to  Griibler,  form  soluble,  crystallizable 
compounds  with  certain  albuminoids,  so  that  these  ele- 
ments, like  potassium,  may  be  concerned  in  the  transport 
of  protein-bodies. 

Silica. — Humphrey  Davy  was  the  first  to  suggest  that 
the  function  of  silica  might  be,  in  case  of  the  grasses, 
sedges,  and  equise'tums,  to  give  rigidity  to  the  slender 
stems  of  these  plants,  and  enable  them  to  sustain  the 
often  heavy  weight  of  the  fruit. 

The  results  of  the  many  experiments  in  water-culture 
by  Sachs,  Knop,  Wolff,  and  others  (see  p.  200),  in  which 
the  supply  of  silica  has  been  reduced  to  an  extremely 
small  amount,  without  detriment  to  the  development  of 
plants,  commonly  rich  in  this  substance,  prove  in  the 
most  conclusive  manner,  however,  that  silica  does  not 
essentially  contribute  to  the  stiffness  of  the  stem. 

Wolff  distinctly  informs  us  that  the  maize  and  oat 
plants  produced  by  him,  in  solutions  nearly  free  from 
silica,  were  as  firm  in  stalk,  and  as  little  inclined  to 
lodge  or  "lay,"  as  those  which  grew  in  the  field. 

*  Common  beans  contain  about  one-fourth  of  one  per  cent  of  mag- 
nesia. 


THE  ASH  OF  PLANTS.  217 

The  "  lodging  "  of  cereal  crops  is  demonstrated  to  re- 
sult from  too  close  a  stand  and  too  little  light,  which 
occasion  a  slender  and  delicate  growth,  and  is  not  per- 
ceptibly influenced  by  presence  or  absence  of  silica. 
Silica,  however,  if  not  necessary  to  the  life  of  the  cereals, 
appears  to  have  an  important  office  in  their  perfect  de- 
velopment under  ordinary  circumstances.  Kreuzhage 
and  Wolff  have  carefully  studied  the  relations  of  silica  to 
the  oat  plant,  using  the  method  of  water-culture.  In  a 
series  of  nine  trials  in  1880,  where,  other  things  being 
equal,  much  silica,  little  silica,  and  no  silica  were  sup- 
plied, the  numbers  of  seeds  produced  were  1,423,  1,039, 
and  715  respectively,  the  corresponding  weights  being 
46,  34,  and  23  grams.  The  total  crops  weighed  196, 
172,  and  168  grams  respectively,  so  that  while  the  yield 
of  seed  was  doubled  in  presence  of  abundant  silica,  the 
total  crop  (dry)  was  increased  in  weight  but  one-sixth. 
The  supply  of  silica  was  accompanied  with  an  absolutely 
diminished  root-formation  as  well  as  by  a  relatively  in- 
creased seed-production.  Similar  trials  in  1881  and  1882 
gave  like  results  (Vs.  St.,  XXX,  p.  161).  Wolff  con- 
cludes that  silica  ensures  the  timely  and  uniform  ripen- 
ing of  the  crop  as  well  as  favors  the  maximum  develop- 
ment of  seed. 

The  natural  supply  of  silica  appears  to  be  always  suf- 
ficient. Application  of  this  substance  in  fertilizers  has 
never  proved  remunerative.  In  those  water-cultures 
where  large  seed-production  has  been  obtained  in  ab 
sence  of  silica,  it  is  probable  that  lime-salts,  phosphates, 
or  other  ash-ingredients,  which  are  commonly  taken  up 
more  abundantly  than  in  field  culture,  have  brought 
about  the  same  result  that  silica  usually  effects.  This 
action  of  the  ash-ingredients  is  apparently  due  to  a  clog- 
ging of  the  cell-tissues  and  consequent  check  of  the  pro- 
cesses of  growth  and  would  seem  to  be  caused  either  by 
the  otherwise  unessential  silica  or  by  an  excess  of  the 


218  HOW  CROPS  GROW. 

ingredients  essential  to  growth.  The  hard,  dense  coat  of 
the  seed  of  the  common  weed  "stone-crop"  (Lithosper- 
mum)  usually  contains  some  13  to  20  per  cent  of  silica 
and  twice  that  amount  of  calcium  carbonate.  Hohnel 
produced  these  seeds  in  water-culture  from  well-grown 
plants  deprived  of  silica  and  found  them  quite  normally 
developed.  The  seed-coat  was  permeated  with  calcium 
carbonate,  which  appears  to  have  fully  replaced  silica 
without  detriment  to  the  plant  (Haberlandt,  Unter- 
suchungen,  II,  p.  160). 

Chlorine. — As  has  been  mentioned,  both  Nobbe  and 
Leydhecker  found  that  buckwheat  grew  quite  well  up  to 
the  time  of  blossom  without  chlorides.  From  that 
period  on,  in  absence  of  chlorides,  remarkable  anomalies 
appeared  in  the  development  of  the  plant.  In  the  ordi- 
nary course  of  growth,  starch,  which  is  organized  in  the 
jnature  leaves,  does  not  remain  in  them  to  much  extent, 
but  is  transferred  to  the  newer  organs,  and  especially  to 
the  fruit,  where  it  often  accumulates  in  large  quantities. 
In  absence  of  chlorides  in  the  experiments  of  Nobbe  and 
Leydhecker,  the  terminal  leaves  becam.  thick  and  fleshy, 
from  extraordinary  development  of  cell-tissue,  at  the 
same  time  they  curled  together  and  finally  fell  off,  upon 
slight  disturbance.  The  stem  became  knotty,  transpira- 
tion of  water  was  suppressed,  the  blossoms  withered 
without  fructification,  and  the  plant  prematurely  died. 
The  fleshy  leaves  were  full  of  starch-grains,  and  it  ap- 
peared that  in  absence  of  chlorine  the  transfer  of  starch 
from  the  foliage  to  the  flower  and  fruit  was  rendered  im- 
possible ;  in  other  words,  chlorine  (in  combination  with 
potassium  or  calcium)  was  concluded  to  be  necessary  to 
—was,  in  fact,  the  agent  of — this  transfer. 

Knop  believes,  however,  that  these  phenomena  are  due 
to  some  other  cause,  and  that  chlorine  is  not  essential  to 
the  perfection  of  the  fruit  of  buckwheat  (see  p.  196). 
J£nop  (Chem.  Centralblatt,  1869,  p.  189)  obtained  some 


THE  ASH  OF  PLANTS.  219 

ripe,  well-developed  buckwheat  seeds  in  chlorine-free 
water-cultures,  while  in  the  same  solutions,  with  addition 
of  chlorides,  other  buckwheat  plants  remained  sterile, 
the  flowers  withering  without  setting  seed.  Knop  states 
that  in  other  trials  maize  and  bean  plants  grew  better 
without  than  with  chlorides.  In  either  case  starch  did 
not  accumulate  in  the  stem  or  leaves  of  maize,  while  all 
the  organs  of  the  bean  were  overloaded  with  starch  both 
in  presence  and  absence  of  chlorides. 

The  experiments  of  Nobbe  and  Leydhecker  are  very 
circumstantially  described  and  have  been  confirmed  by 
the  later  work  of  Nobbe,  Schroder,  and  Erdmann  (  Vs, 
St.,  XIII,  pp.  392-6).  See  p.  196. 

Iron. — We  are  in  possession  of  some  interesting  facts, 
which  throw  light  upon  the  function  of  this  metal  in  the 
plant.  In  case  of  the  deficiency  of  iron,  foliage  loses  its 
natural  green  color,  and  becomes  pale  or  white  even  in 
the  full  sunshine.  In  absence  of  iron  a  plant  may  un- 
fold its  buds  at  the  expense  of  already  organized  matters, 
as  a  potato-sprout  lengthens  in  a  dark  cellar,  or  in  the 
manner  of  fungi  and  white  vegetable  parasites  ;  but  the 
leaves  thus  developed  are  incapable  of  assimilating  carbon, 
and  actual  growth  or  increase  of  total  weight  is  impossi- 
ble. Salm-Horstmar  showed  (1849)  that  plants  which 
grow  in  soils  or  media  destitute  of  iron  are  very  pale  in 
color,  and  that  addition  of  iron-salts  very  speedily  gives 
them  a  healthy  green.  Sachs  found  that  maize-seed- 
lings, vegetating  in  solutions  free  from  iron,  had  their 
first  three  or  four  leaves  green ;  several  following  were 
white  at  the  base,  the  tips  being  green,  and  afterward 
perfectly  white  leaves  unfolded.  On  adding  a  few  drops 
of  sulphate  or  chloride  of  iron  to  the  nourishing  medium, 
the  foliage  was  plainly  altered  within  twenty-four  hours, 
and  in  three  to  four  days  the  plant  acquired  a  deep,  lively 
green.  Being  afterwards  transferred  to  a  solution  desti- 
tute of  iron,  perfectly  white  leaves  were  again  developed, 


220  HOW  CROPS  GROW. 

and  these  were  brought  to  a  normal  color  by  addition  of 
iron. 

E.  Gris  was  the  first  to  trace  the  reason  of  these  effects, 
and  first  found  (in  1843)  that  watering  the  roots  of 
plants  with  solutions  of  iron,  or  applying  such  solutions 
externally  to  the  leaves,  shortly  developed  a  green  color 
where  it  was  previously  wanting.  By  microscopic  stud- 
ies he  found  that,  in  the  absence  of  iron,  the  protoplasm 
of  the  leaf-cells  remains  a  colorless  or  yellow  mass,  desti- 
tute of  visible  organization.  Under  the  influence  of  iron, 
grains  of  chlorophyl  begin  at  once  to  appear,  and  pass 
through  the  various  stages  of  normal  development.  We 
know  that  the  power  of  the  leaf  to  decompose  carbon 
dioxide  and  assimilate  carbon  resides  in  the  cells  that 
contain  chlorophyl,  or,  we  may  say,  in  the  chlorophyl- 
grains  themselves.  We  understand  at  once,  then,  that 
in  the  absence  of  iron,  which  is  essential  to  the  forma- 
tion of  chlorophyl,  there  can  be  no  proper  growth,  no 
increase  at  the  expense  of  the  external  atmospheric  food 
of  vegetation. 

Risse,  under  Sachs's  direction  (Exp.  Physiologic,  p. 
143),  demonstrated  that  manganese  cannot  take  the  place 
of  iron  in  the  office  just  described. 


CHAPTER  HI. 

o     J.# 

4TTANTITATIVE     RELATIONS    AMONG    THE     INGREDIENTS 
OF    PLANTS. 

Various  attempts  have  been  made  to  exhibit*  definite 
numerical  relations  between  certain  different  ingredients 
of  plants. 

Equivalent  Replacement  of  Bases. — In  1840,  Lie- 
big,  io  his  Chemistry  applied  tQ  Agriculture,  suggested 


QUANTITATIVE   RELATIONS.  221 

that  the  various  bases  or  basic  metals  might  displace 
each  other  in  equivalent  quantities,  i.  e. ,  in  the  ratio  of 
their  molecular  or  atomic  weights,  and  that,  were  such 
the  case,  the  discrepancies  to  be  observed  among  analyses 
should  disappear,  if  the  latter  were  interpreted  on  this 
view.  Liebig  instanced  two  analyses  of  the  ashes  of  fir- 
wood  and  two  of  pine-wood  made  by  Berthier  and  Saus- 
sure,  as  illustrations  of  the  correctness  of  this  theory. 
In  the  fir  of  Mont  Breven,  carbonate  of  magnesium  was 
present  ;  in  that  of  Mont  La  Salle,  it  was  absent.  In 
the  former  existed  but  half  as  much  carbonate  of  potas- 
sium as  in  the  latter.  In  both,  however,  the  same  total 
percentage  of  carbonates  was  found,  and  the  amount  of 
oxygen  in  the  bases  was  the  same  in  both  instances. 

Since  the  unlike  but  equivalent  quantities  of  potash, 
lime,  and  magnesia  contain  the  same  quantity  of  oxy- 
gen, these  oxides,  in  the  case  in  question,  really  replaced 
each  other  in  equivalent  proportions.  The  same  was 
true  for  the  ash  of  pine-wood,  from  Allevard  and  from 
Norway.  On  applying  this  principle  to  other  cases  it 
has,  however,  signally  failed.  The  fact  that  the  plant 
can  contain  accidental  or  unessential  ingredients  ren- 
ders it  obvious  that,  however  truly  such  a  law  as  that  of 
Liebig  may  in  any  case  apply  to  those  substances  which 
are  really  concerned  in  the  vital  actions,  it  will  be  impos- 
sible to  read  the  law  in  the  results  of  analyses. 

Relation  of  Phosphates  to  Albuminoids. — Liebig 
likewise  considered  that  a  definite  relation  exists  be 
tween  the  phosphoric  acid  and  the  albuminoids  of  the 
ripe  grains.  That  this  relation  is  not  constant  is  evi- 
dent from  the  following  statement  of  data  bearing  on 
the  question.  In  the  table,  the  amount  of  nitrogen  (N), 
representing  the  albuminoids  (see  p.  113),  found  in  vari- 
ous analyses  of  rye  and  wheat  grain,  is  compared  with 
that  of  phosphoric  acid  (P205),  the  latter  being  taken  as 
unity.  The  ratios  of  P?06  to  $"  were  fpumJ  to  ra.nge  a.s 
follows ; 


223  HOW  CBOPS  GROW. 


PA- 


In  7  Samples  of  Rye-kernel  by  Fehling  &  Faiszt 1 : 1.97—3.06 

"  11  "                       "                    Mayer 1:2.04—2.38 

««  5  «•                      "                    Bibra 1:1.68—2.81 

"  6  "                      "                    Siegert 1:2.35—2.96 

"  28  "  "            the  extreme  range  was  from....  1: 1.68— 3.06 

«'  2  "            Wheat-kernel  by  Fehling  &  Faiszt 1:2.71—2.86 

•'  11  "                      '•                         Mayer 1:1.83- -2.19 

«•  2  ««                      ••                         Zoeller 1:2.02—2.16 

••  30  «•                      "                        Bibra ..1:1.87—3.55 

«  6  "         "           u                        Siegert ..1:2.30—3.33 

••  61  "  "           "             the  extreme  range  was  from....  1:1.83— 3.55 

Siegert,  who  collected  these  data  (  Vs.  St.,  Ill,  p.  147), 
and  who  experimented  on  the  influence  of  phosphatic  and 
nitrogenous  fertilizers  upon  the  composition  of  wheat  and 
rye,  gives  as  the  general  result  of  his  special  inquiries  that 
Phosphoric  acid  and  Nitrogen  stand  in  no  constant  rela- 
tion to  each  other.  Nitrogenous  manures  increase  the  per 
cent  of  nitrogen  and  diminish  that  of  phosphoric  acid. 

Other  Relations. — All  attempts  to  trace  simple  and 
constant  relations  between  other  ingredients  of  plants, 
viz.,  between  starch  and  alkalies,  cellulose  and  silica,  etc., 
jxaye  proved  fruitless. 

It  is  much  rather  demonstrated  that  the  proportion  of 
the  constituents  is  constantly  changing  from  day  to  day  as 
the  relative  mass  of  the  individual  organs  themselves  un- 
dergoes perpetual  variation. 

In  adopting  the  above  conclusions  it  is  not  asserted  that 
such  genetic  relations  between  phosphates  and  albumin- 
oids, or  between  starch  and  alkalies,  as  Liebig  first  sug- 
gested and  as  various  observers  have  labored  to  show,  do 
not  exist,  but  simply  that  they  do  not  appear  from  the 
analyses  of  plants. 

§2. 

THE  COMPOSITION  OF  THE  PLANT  IN  SUCCESSIVE    STAGES 
OF  GROWTH. 

We  have  hitherto  regarded  the  composition  of  the  plant 
mostly  in  a  relative  sense,  and  have  instituted  no  compar- 


223 


isons  between  the  absolute  quantities  of  its  ingredients  at 
different  stages  of  growth.  We  have  obtained  a  series  of 
isolated  views  of  the  chendstry  of  the  entire  plant,  or  of 
its  parts  at  some  certain  period  of  its  life,  or  when  placed 
under  certain  conditions,  and  have  thus  sought  to  ascer- 
tain the  peculiarities  of  these  periods,  and  to  estimate  the 
influence  of  these  conditions.  It  now  remains  to  attempt 
in  some  degree  the  combination  of  these  sketches  into  a 
panoramic  picture — to  give  an  idea  of  the  composition 
of  the  plant  at  the  successive  steps  of  its  development. 
We  shall  thus  gain  some  insight  into  the  rate  and  manner 
of  its  growth,  and  acquire  data  that  have  an  important 
bearing  on  the  requisites  for  its  perfect  nutrition.  For 
this  purpose  we  need  to  study  not  only  the  relative 
(percentage)  composition  of  the  plant  and  of  its  parts  at 
various  stages  of  its  existence,  but  we  must  also  inform 
ourselves  as  to  the  total  quantities  of  each  ingredient  at 
these  periods. 

We  shall  select  from  the  data  at  hand  those  which 
illustrate  the  composition  of  the  oat-plant.  Not  only  the 
ash-ingredients,  but  also  the  organic  constituents,  will  be 
noticed  so  far  as  our  information  and  space  permit. 

The  Composition  and  Growth  of  the  Oat-Plant 
may  be  studied  as  a  type  of  an  important  class  of  agricul- 
tural plants,  viz. :  the  annual  cereals — plants  which  com- 
plete their  existence  in  one  summer,  and  which  yield  a 
large  quantity  of  nutritious  seeds — the  most  valuable  re- 
sult of  culture.  The  oat-plant  was  first  studied  in  its 
various  parts  and  at  different  times  of  development  by 
Prof.  John  Pitkin  Norton,  of  Yale  College.  His  labori- 
ous research  published  in  1846  ( Trans.  Highland  and  Ag. 
Soc.,  1845-7,  also  Am.  Jour.  ofSci.  andArts,N(A.  3, 1847) 
was  the  first  step  in  advance  of  the  single  and  disconnected 
analyses  which  had  previously  been  the  only  data  of  the 
agricultural  physiologist.  For  several  reasons,  however, 
the  work  of  Norton  was  imperfect.  The  analytic  metli- 


224  HOW  CROPS  GROW. 

ods  employed  by  him,  though  the  best  in  use  at  that  day, 
and  handled  by  him  with  great  skill,  were  not  adapted  to 
furnish  results  trustworthy  in  all  particulars.  Fourteen 
years  later,  Arendt*  at  Moeckern,  and  Bretschneiderf  at 
Saarau,  in  Germany,  at  the  same  time,  but  independently 
of  each  other,  resumed  the  subject,  and  to  their  labors 
the  subjoined  figures  and  conclusions  are  due. 

Here  follows  a  statement  of  the  Periods  at  which  the 
plants  were  taken  for  analysis  : 

[still  closed, 
lot  -peTir.H  I  June  18,  Arendt— Three  lower  leaves  unfolded,  two  upper 

JU  J     "      19,  Bretschneider— Four  to  five  leaves  developed. 
<>i\     •Porinri  1  June  30,  (12  clays),  Arendt— Shortly  before  full  heading. 

JU  }     "       29,  (10  days),  Bretschneider— The  plants  were  headed. 
o/i    T>*r*^A  I  July  10,  (10  days),  Arendt— Immediately  after  bloom. 

)a  }     "        8,  (  9  days),  Bretsclmeider— Full  bloom. 
4th  pprirwi  \  July  21»  (n  days)>  Arendt— Beginning  to  ripen. 

30 )      "      28,  (20  days),  Bretschneider—    "  " 

fith  Vpriodljuly  31'  (10  days),  Arendt— Fully  ripe. 

M I  Aug.    6,  (  9  days),  Bretschneider— Fully  ripe. 

It  will  be  seen  that  the  periods,  though  differing  some- 
what as  to  time,  correspond  almost  perfectly  in  regard  to 
the  development  of  the  plants.  It  must  be  mentioned 
that  Arendt  carefully  selected  luxuriant  plants  of  equal 
size,  so  as  to  analyze  a  uniform  material  (see  p.  171), 
and  took  no  account  of  the  yield  of  a  given  surface  of  soil. 
Bretschneider,  on  the  other  hand,  examined  the  entire 
produce  of  a  square  rod.  The  former  procedure  is  best 
adapted  to  study  the  composition  of  the  well-nourished 
individual  plant;  the  latter  gives  a  truer  view  of  the  crop. 

The  unlike  character  of  the  material  as  just  indicated 
is  but  one  of  the  various  causes  which  might  render  the 
two  series  of  observations  discrepant.  Thus,  differences 
in  soil,  weather  and  seeding,  would  necessarily  influence 
the  relative  as  well  as  the  absolute  development  of  the  two 
crops.  The  results  are,  notwithstanding,  strikingly  ac- 
cordant in  many  particulars.  In  all  cases  the  roots  were 
not  and  could  not  be  included  in  the  investigation,  as  it 
is  impossible  to  free  them  from  adhering  soil. 

*  Das  Wa.c.hsthum  der  Haferpfln.nze,  Leipzif/,  1859. 

t  WachsthumsverhMtnisse  der  Haferyflanze,  Jour./ur  Prakt.  Chem.,  76, 
193. 


COMPOSITION  12?  SUCCESSIVE  STAGES.  225 

The  Total  Weight  of  Crop  per  English  acre,  at  the 
end  of  each  period,  was  as  follows: 

TABLE  I.—Bretschneider. 
1st    Period,  6,358  Ibs.  avoirdupois* 
2d        "        10,603  "  «• 

3d        "        16,623  "  «« 

4th       "        14,981- «  «« 

5th        "         10,622   "  «« 

The  Total  Weights  of  Water  and  Dry  Matter  for 

all  but  the  2d  Period — the  material  of  which  was  acci- 
dentally lost — were: 

TABLE  Il.—Bretschneider. 

Dry  Matter,  Water, 

Ibs.  av.  per  acre.  Ibs.  av.  per  acre. 

1st    Period,                    1,284  5,074 

2d<&3d"                           4,383  12,240 

4th          "                           5,427  9,554 

5th         •«                          6,886  3,736 

1. — From  Table  I  it  is  seen:  That  the  weight  of  the 
live  crop  is  greatest  at  or  before  the  time  of  blossom.* 
After  this  period  the  total  weight  diminishes  as  it  had 
previously  increased. 

2. — From  Table  II  it  becomes  manifest:  That  the  organ- 
•ic  tissue  (dry  matter)  continually  increases  hi  quantity  up 
to  the  maturity  of  the  plant;  and 

3. — The  loss  after  the  3d  Period  falls  exclusively  upon 
the  water  of  vegetation.  At  the  time  of  blossom  the 
plant  has  its  greatest  absolute  quantity  of  water,  while 
its  least  absolute  quantity  of  this  ingredient  is  found  when 
it  is  fully  ripe. 

By  taking  the  difference  between  the  weights  of  any 
two  Periods,  we  obtain: 

The  Increase  or  Loss  of  Dry  Matter  and  Water 
during  each  Period. 

TABLE  m.—Bretschneider. 

Dry  Matter,  Water, 

Ibs  per  acre.  Ibs  per  acre. 

1st  Period,  (58  days),    1,284  Gain.  5,074  Gain. 

2d&3d"       (19  days),    3,09§     "  7,166     " 
4th         "       (20  days),    1,044     "  2,686  Loss. 

5th         "       (  S  days),    1,456     "  5,818     * 

*In  Areiidt's  Experiment,  at  the  time  ef  "J«ia*Uiig  out?"  3d -Period 

15 


226  HOW  CROPS  GROW. 

On  dividing  the  above  quantities  by  the  number  of  days 
of  the  respective  periods,  there  results: 

The  Average  Daily  Gain  or  Loss  per  Acre  during 
each  Period. 

TABLE  IV.—Bretschneider. 

Dry  Matter.  Water. 

1st     Period,     22  Ibs.  Gain.     87  Ibs.  Gain. 
2d  &  3d  "  163    "        ««         377    "        " 

4th          "  52    "       "         134    "    Loss. 

5th  "  162    "        "         646    "       «« 

4. — Table  III.,  and  especially  Table  IV,  show  that  the 
gain  of  organic  matter  in  Bretschneider's  oat-crop  went 
on  most  rapidly  at  or  before  the  time  of  blossom  (accord- 
ing to  Arendt  at  the  time  of  heading  out).  This  was,  then, 
the  period  of  most  active  growth.  Afterward  the  rate  of 
growth  diminished  by  more  than  one-half,  and  at  a  later 
period  increased  again,  though  not  to  the  maximum. 

Absolute  Quantities  of  Carbon,  Hydrogen,  Oxy- 
gen, Nitrogen  (Organic  Matter),  and  Ash  in  the  dry 
oat-crop  at  the  conclusion  of  the  several  periods  (Ibs. 
per  acre) : 

TABLE  V.—Sretschneider. 

Carbon.    Hydrogen.    Oxygen.  Nitrogen.  Ash.* 

1st     Period,                  593              80                455  46  110 

2d  &  3d  "                       2,137             286              1,575  122  263 

4th           "                        2,600             343               2,043  150  291 

5th          "                       3,229             405              2,713  167  372 

Amounts  of  Carbon,  Hydrogen,  Oxygen,  Nitro- 
gen, and  Ash-ingredients  assimilated  by  the  oat-crop 
during  the  several  periods.  Water  of  vegetation  is  not 
included  (Ibs.  per  acre)  : 

TABLE  VI.—Bretschneider. 

Nitrogen.  AtMngredients. 
46  110 

76  153 

28  28 

17  81 

*  In  Bretschneider's  analyses,  "  ash  "  signifies  the  residue  left  after 
carefully  burning  the  plant.  In  Arendrs  investigation  the  sulphur 
and  chlorine  were  determined  in  the  unburned  plant. 


1st    Period, 

Carbon. 
593 

Hydrogen. 
80 

Oxygen. 
455 

2d&3d  " 

1,544 

206 

1,575 

4th          " 

453 

57 

468 

5th           " 

629 

62 

670 

COMPOSITION  IN  SUCCESSIVE  STAGES.  22? 

Relative  Quantities  of  Carbon,  Hydrogen,  Oxy- 
gen, Nitrogen  (Organic  Matter)  and  Ash  in  the  dry 
oat-crop,  at  the  end  of  the  several  periods  (per  cent) : 

TABLE  VII.— Bretschneider. 

Carbon.       Hydrogen.      Oxygen.     Nitrogen.  (Organic  Matter.)  Ash. 

1st      Period,      46.22              6.23             35.39           3.59  91.43               8.57 

2d  &  3d  "             48.76              6.53             35.96           2.79  94.04               5.96 

4th           "            47.91               6.33             37.65           2.78  94.67               5.33 

5th           "             46.89              5.88             39.40           2.43  94.60               5.40 

Relative  Quantities  of  Carbon,  Hydrogen,  Oxy- 
gen, and  Nitrogen,  in  dry  substance,  after  deducting 
the  somewhat  variable  amount  of  ash  (per  cent)  : 
TABLE  VIII. — Bretschneider. 
Carbon.  Hydrogen.  Oxygen.         Nitrogen. 

1st      Period,  50.55  6.81  38.71  3.93 

2d  &  3d  "  51.85  6.95  38.24  2.86 

4th  "  50.55  6.96  39.83  2.93 

5th  "  49.59  6.21  41.64  2.56 

5.  The  Tables  V,  VI,  VII,  and  VIII,  demonstrate  that 
while  the  absolute  quantities  of  the  elements  of  the  dry 
oat-plant  continually  increase  to  the  time  of  ripening, 
they  do  not  increase  in  the  same  proportion.  In  other 
words,  the  plant  requires,  so  to  speak,  a  change  of  diet 
as  it  advances  in  growth.  They  further  show  that  nitro- 
gen and  ash  are  relatively  more  abundant  in  the  young 
than  in  the  mature  plant ;  in  other  words,  the  rate  of 
assimilation  of  Nitrogen  and  fixed  ingredients  falls  be- 
hind that  of  Carbon,  Hydrogen,  and  Oxygen.  Still  oth- 
erwise expressed,  the  plant  as  it  approaches  maturity 
organizes  relatively  more  carbhydrates  and  less  albu- 
minoids. 

The  relations  just  indicated  appear  more  plainly  when 
we  compare  the  Quantities  of  Nitrogen,  Hydrogen,  and 
Oxygen,  assimilated  during  each  period,  calculated  upon 
the  amount  of  Carbon  assimilated  in  the  same  time  and 
assumed  at  100. 

TABLE  IX.— Bretschneider. 

Carbon.  Nitrogen.         Hydrogen.  Oxygen. 

1st     Period,  100  7.8  13.4  73.6 

2d&3d"  100  4.9  13.3  72.5 

4th  "  100  6.1  12.3  100.8 

6th  "  100  2.6  10.6  100.6 


228  HOW  CROPS  GROW. 

From  Table  IX  we  see  that  the  ratio  of  Hydrogen  to 
Carbon  regularly  diminishes  as  the  plant  matures ;  that 
of  Nitrogen  falls  greatly  from  the  infancy  of  the  plant  to 
the  period  of  full  bloom,  then  strikingly  increases  during 
the  first  stages  of  ripening,  but  falls  off  at  last  to  mini- 
mum. The  ratio  of  Oxygen  to  Carbon  is  the  same  during 
the  1st,  3d,  and  3d  Periods,  but  increases  remarkably 
from  the  time  of  full  blossom  until  the  plant  is  ripe. 

As  already  stated,  the  largest  absolute  assimilation  of 
all  ingredients — most  rapid  growth — takes  place  at  the 
time  of  heading  out,  or  blossom.  At  this  period  all  the 
volatile  elements  are  assimilated  at  a  nearly  equal  rate, 
and  at  a  rate  similar  to  that  at  which  the  fixed  matters 
(ash)  are  absorbed.  In  the  first  period  Nitrogen  and 
Ash ;  in  the  4th  Period,  Nitrogen  and  Oxygen ;  in  the 
5th  Period,  Oxygen  and  Ash  are  assimilated  in  largest 
proportion. 

This  is  made  evident  by  calculating  for  each  period  the 
relative  average  daily  increase  of  each  ingredient,  the 
amount  of  the  ingredients  in  the  ripe  plant  being  assumed 
at  100,  as  a  point  of  comparison.  The  figures  resulting 
from  such  a  calculation  are  given  in 

TABLE  X.—£retschneider. 

Carbon.      Hydrogen.       Oxygen.  JfUrogen.  Ash. 

1st         Period,         0.31  0.33  0.28  0.47  0.50 

2dand3d  "  2.51  2.68  2.17  2.39  2.13 

4th  "  0.89  0.88  1.07  1.06  0.47 

5th  "  1.49  1.16  1.89  0.75  1.70 

The  increased  assimilation  of  the  5th  over  the  4th 
Period  is,  in  all  probability,  only  apparent.  The  results 
of  analysis,  as  before  mentioned,  refer  only  to  those  parts 
of  the  plant  that  are  above  ground.  The  activity  of  the 
foliage  in  gathering  food  from  the  atmosphere  is  doubt- 
less greatly  diminished  before  the  plant  ripens,  as  evi- 
denced by  the  leaves  turning  yellow  and  losing  water  of 
vegetation.  The  increase  of  weight  in  the  plant  above 
ground  probably  proceeds  from  matters  previously  stored 


COMPOSITION  IN  SUCCESSIVE  STAGES.  229 

in  the  roots,  which  now  are  transferred  to  the  fruit  and 
foliage,  and  maintain  the  growth  of  these  parts  after 
their  power  of  assimilating  inorganic  food  (C02,  H20, 
NH3,  1ST205)  is  lost. 

The  following  statement  exhibits  the  absolute  average 
daily  increase  of  Carbon,  Hydrogen,  Oxygen,  Nitrogen,  and 
Ash,  during  the  several  periods  (Ibs.  per  acre)  : 

TABLE  XI.—Bretschneider. 

.  Carbon.  Hydrogen.  Oxygen.  Nitrogen.  Ath. 

1st  Period,  10.0  1.4  7.8  0.8  1.9 

2dand3d  "  81.0  10.8  83.0  4.0  8.0 

4th  "  22.6  2.9  23.4  1.4  1.4 

6th  "  70.0  6.9  74.4  1.9  9.0 

Turning  now  to  Arendt's  results,  which  are  carried 
more  into  detail  than  those  of  Bretschneider,  we  will 
notice: 

A. — The  Relative*  (percentage]  Composition  of  the 
Entire  Plant  and  of  its  Parts*  during  the  several 
periods  of  vegetation. 

1.  Fiber  \  is  found  in  greatest  proportion — 40  per  cent 
— in  the  lower  joints  of  the  stem,  and  from  the  time 
when  the  grain  "heads  out,"  to  the  period  of  bloom. 
Relatively  considered,  there  occur  great  variations  in  tha 
same  part  of  the  plant  at  different  stages  of  growth. 
Thus,  in  the  ear,  which  contains  the  least  fiber,  the 
quantity  of  this  substance  regularly  diminishes,  not 
absolutely,  but  only  relatively,  as  the  plant  becomes 
older,  sinking  from  27  per  cent  at  heading  to  12  per 
cent  at  maturity.  In  the  leaves,  which,  as  regards 
fiber,  stand  intermediate  between  the  stem  and  ear,  this 

*  Aremlt  selected  large  and  well-developed  plants,  divided  them  into 
six  parts,  and  analyzed  each  part  separately.  His  divisions  of  the 
plants  were:  1,  the  three  lowest  joints  of  the  stem;  2,  the  two  middle 
joints;  3,  the  upper  joint;  4,  the  three  lowest  leaves;  5,  the  two  upper 
leaves;  6,  the  ear.  The  stems  were  cut  just  above  the  nodes,  the  leaves 
included  the  sheaths,  the  ears  were  stripped  from  the  stem.  Arendt 
rejected  all  plants  which  were  not  perfect  when  gathered.  When 
nearly  ripe,  the  cereals,  as  is  well  known,  often  lose  one  or  more  of 
their  lower  leaves.  For  the  numerous  analyses  on  which  these  conclu- 
sions are  based  we  must  refer  to  the  original. 

t  L  e.,  Crude  cellulose;  see  p.  45. 


230  HOW  CEOPS  GROW. 

substance  ranges  from  22  to  38  per  cent.  Previous  to 
blossom,  the  upper  leaves,  afterwards  the  lower  leaves, 
are  the  richest  in  fiber.  In  the  lower  leaves  the  maxi- 
mum (33  per  cent)  is  found  in  the  fourth  ;  in  the  upper 
leaves  (38  per  cent),  in  the  second  period. 

The  apparent  diminution  in  amount  of  fiber  is  due  in 
all  cases  to  increased  production  of  other  ingredients. 

2.  Fat  and  Wax  are  least  abundant  in  the  stem.     Their 
proportion  increases,  in  general,  in  the  upper  parts  of  the 
stem  as  well  as  during  the  latter  stages  of  its  growth.  The 
range  is  from  0.2  to  3  per  cent.     In  the  ear  the  propor- 
tion increases  from  2  to  3. 7  per  cent.    In  the  leaves  the 
quantity  is  much  larger  and  is  mostly  wax  with  little  fat. 
The  smallest  proportion  is  4.8  per  cent,  which  is  found  in 
the  upper  leaves  when  the  plant  is  ripe.     The  largest 
proportion,  10  per  cent,  exists  in  the  lower  leaves,  at  the 
time   of  blossom.     The  relative  quantities  found  in  the 
leaves  undergo  considerable  variation  from  one  stage  of 
growth  to  another. 

3.  Non-nitrogenous  matters,  other  than  fiber,  viz.,  starch, 
sugars,  gums,  etc.,*  undergo  great  and  irregular  variation. 
In  the  stem  the  largest  percentage  (57  per  cent)  is  found 
in  the  young  lower  joints;  the  smallest  (43  per  cent)  in 
ripe  upper  straw.    Only  in  the  ear  occurs  a  regular  in- 
crease, viz.,  from  54  to  63  per  cent. 

4.  The  albuminoids,  f  in  Arendt's  investigation,  exhibit 
a  somewhat  different  relation  to  the  vegetable  substance 
from  what  was  observed  by  Bretschneider,  as  seen  from 
the  subjoined  comparison  of  the  percentages  found  at 
the  different  periods  : 

PERIODS. 

i.        ii.       in.      rv.       v. 

Arendt 20.93       11.65       10.86       13.67       14.30 

Bretschneider 22.73  17.67       17.61       15.39 

*  What  remains  after  deducting  fat  and  wax,  albuminoids,  fiber  and 
ash,  from  the  dry  substance,  is  here  included. 
t  Calculated  by  multiplying  the  percentage  of  nitrogen  by  6.33. 

These  differences  may  be  variously  accounted  for.  They 


COMPOSITION  IN  SUCCESSIVE   STAGES. 


231 


are  due,  in  part,  to  the  fact  that  Arendt  analyzed  only 
large  and  perfect  plants.  Bretschneider,  on  the  other 
hand,  examined  all  the  plants  of  a  given  plot,  large  and 
small,  perfect  and  injured.  The  differences  illustrate 
what  has  been  already  insisted  on,  viz.,  that  the  develop- 
ment of  the  plant  is  greatly  modified  by  the  circum- 
stances of  its  growth,  not  only  in  reference  to  its  exter- 
nal figure,  but  also  as  regards  its  chemical  composition. 

The  relative  distribution  of  nitrogen  in  the  parts  of  the 
plant  at  the  end  of  the  several  periods  is  exhibited  by  the 
following  table,  simple  inspection  of  which  shows  the 
fluctuations  (relative)  in  the  content  of  this  element.  The 
percentages  are  arranged  for  each  period  separately,  pro- 
ceeding from  the  highest  to  the  lowest : 


PERIODS. 


I. 

II.                     III. 

IV. 

V. 

Upper  leaves. 

Lower  leaves.  Upper  leaves. 

Ears. 

Ears. 

3.74 

2.3i) 

2.27 

2.85 

3.04 

Lower  leaves. 

Upper  leaves. 

Lower  leaves. 

Upper  leaves. 

Upper  leaves. 

3.38 

2.19 

2.18 

1.91 

1.74 

Lower  leaves. 

Ears. 

Ears. 

Lower  leaves. 

Upper  stem. 

2.15 

2.06 

1.85 

1.62 

1.56 

Middle  stem. 

Upper  stem. 

Upper  stem. 

Lower  leaves. 

1.52 

1.34 

1.60 

1.43 

Upper  stem. 

Middle  stem. 

Middle  stem. 

Middle  stem. 

0.87 

0.98 

1.20 

1.17 

Lower  stem. 

Lower  stem. 

Lower  stem. 

Lower  stem. 

0.80 

0.88 

0.83 

0.79 

5.  Ash. — The  agreement  of  the  percentages  of  ash  in 
the  entire  plant,  in  corresponding  periods  of  the  growth 
of  the  oat,  in  the  independent  examinations  of  Bret- 
schneider and  Arendt,  is  remarkably  close,  as  appears 
from  the  figures  below  : 


Bretschneider 8.57 

Arendt...  ...8.03 


II. 


5.24 


PERIODS. 
III. 
5.96 
5.44 


IV. 

5.33 
5.20 


V. 

5.40 
5.17 


As  regards  the  several  parts  of  the  plant,  it  was  found 
by  Arendt  that,  of  the  stem,  the  upper  portion  was  richest 
in  ash  throughout  the  whole  period  of  growth.  Of  the 
leaves,  on  the  contrary,  the  lower  contained  most  fixed 
matters.  In  the  ear  there  occurred  a  continual  decrease 


232  HOW  CROPS  GROW. 

from  its  first  appearance  to  its  maturity,  while  in  the 
stem  and  leaves  there  was,  in  general,  a  progressive 
increase  towards  the  time  of  ripening.  The  greatest 
percentage  (10.5  per  cent)  was  found  in  the  ripe  leaves; 
the  smallest  (0.78  per  cent)  in  the  ripe  lower  straw. 

Far  more  interesting  and  instructive  than  the  relative 
proportions  are 

B. — The  Absolute  Quantities  of  the  Ingredients 
found  in  the  Plant  at  the  conclusion  of  the  sev- 
eral periods  of  growth. — These  absolute  quantities, 
as  found  by  Arendt,  in  a  given  number  of  carefully- 
selected  and  vigorous  plants,  do  not  accord  with  those 
obtained  by  Bretsclmeider  from  a  given  area  of  ground, 
nor  could  it  be  expected  that  they  should,  because  it  is 
next  to  impossible  to  cause  the  same  amount  of  vegeta- 
tion to  develop  on  a  number  of  distinct  plots. 

Though  the  results  of  Bretschneider  more  nearly  rep- 
resent the  crop  as  obtained  in  farming,  those  of  Arendt 
give  a  truer  idea  of  the  plant  when  situated  in  the  best 
possible  conditions,  and  attaining  a  uniformly  high 
development.  We  shall  not  attempt  to  compare  the  two 
sets  of  observations,  since,  strictly  speaking,  in  most 
points  they  do  not  admit  of  comparison. 

From  a  knowledge  of  the  absolute  quantities  of  the 
substances  contained  in  the  plant  at  the  ends  of  the  several 
periods,  we  may  at  once  estimate  the  rate  of  growth,  i.  e., 
the  rapidity  with  which  the  constituents  of  the  plant  are 
either  taken  up  or  organized. 

The  accompanying  table,  which  gives  in  alternate  col- 
umns the  total  weights  of  1,000  plants  at  the  end  of  the 
several  periods,  and  (by  subtracting  the  first  from  the 
second,  the  second  from  the  third,  etc.)  the  gain  from 
matters  absorbed  or  produced  during  each  period,  will 
serve  to  justify  the  deductions  that  follow,  which  are 
taken  from  the  treatise  of  Arendt,  and  which  apply,  of 
course,  only  to  the  plants  examined  by  this  investigator. 


COMPOSITION  IN  SUCCESSIVE  STAGES. 


233 


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234  HOW  CBOPS  GROW. 

1.  The  plant  increases  in  total  weight  (dry  matter) 
through  all  its  growth,  but  to  unequal  degrees  in  differ- 
ent periods.     The  greatest  growth  occurs  at  the  time  of 
heading  out ;  the  slowest,  within  ten  days  of  maturity. 

We  may  add  that  the  increase  of  the  oat  after  blossom 
takes  place  mostly  in  the  seed,  the  other  organs  gaining 
but  little.  The  lower  leaves  almost  cease  to  grow  after 
the  3d  Period. 

2.  Fiber  is  produced  most  largely  at  the  time  of  head- 
ing out  (3d  Period).     When  the  plant  has  finished  blos- 
soming  (end  of   3d    Period),   the   formation  of   fiber 
entirely  ceases.     Afterward  there  appears  to  occur  a 
slight  diminution  of  this  substance,  more  probably  due 
to  unavoidable  loss  of  lower  leaves  than  to  a  resorption 
or  metamorphosis  in  the  plant. 

3.  Fat  is  formed  most  largely  at  the  time  of  blossom. 
It  ceases  to  be  produced  some  weeks  before  ripening. 

4.  Albuminoids  are  very  irregular  in  their  formation. 
The  greatest  amount  is  organized  during  the  4th  Period 
(after  blossoming).     The  gain  in  albuminoids  within 
this  period  is  two-fifths  of  the  total  amount  found  in  the 
ripe  plant,  and  also  is  nearly  two-fifths  of  the  entire  gain 
of  organic  substance  in  tb,e  same  period.     The  absolute 
amount  organized  in  the  1st  Period  is  not  much  less 
than  in  the  4th,  but  in  the  3d,  3d  and  5th  Periods  the 
quantities  are  considerably  smaller. 

Bretschneider  gives  the  data  for  comparing  the  pro- 
duction of  albuminoids  in  the  oat  crop  examined  by  him 
with  Arendt's  results.  Taking  the  quantity  found  at 
the  conclusion  of  the  1st  Period  as  100,  the  amounts 
gained  during  the  subsequent  periods  are  related  as 
follows: 

PERIODS. 

I.        II.     III.    (II.  &  III.)    IV.  (II.,  III.  &  IV.)  V. 

Arendt 100       67       46          (113)  120  (233)  36 

Bretschneider  .100       ?        ?  (165)         •  62  (22T)  35 

We  perceive  striking  differences  in  the  comparison.    In 


COMPOSITION  IN  SUCCESSIVE  STAGES.  235 

Bretschneider's  crop  the  increase  of  albuminoids  goes  on 
most  rapidly  in  the  3d  and  3d  Periods,  and  sinks  rapidly 
during  the  time  when  in  Arendt's  plants  it  attained  the 
maximum.  Curiously  enough,  the  gain  in  the  3d,  3d 
and  4th  Periods,  taken  together,  is  in  both  cases  as  good 
as  identical  (233  and  227),  and  the  gain  during  the  last 
period  is  also  equal.  This  coincidence  is  doubtless,  how- 
ever, merely  accidental.  Comparisons  with  other  crops 
of  oats  examined,  though  much  less  completely,  by 
Stockhardt  (Chemischer  Ackersmann,  1855)  and  Wolff 
(Die  Erschopfung  des  Bodens  durch  die  Cultur,  1856) 
demonstrate  that  the  rate  of  assimilation  is  not  related 
to  any  special  times  or  periods  of  development,  but 
depends  upon  the  stores  of  food  accessible  to  the  plant 
and  the  favor  of  the  weather,  or  other  external  conditions. 

The  following  figures,  which  exhibit  for  each  period 
of  both  crops  a  comparison  of  the  gain  in  albuminoids 
with  the  increase  of  the  other  organic  matters,  further 
strikingly  demonstrate  that,  in  the  act  of  organization, 
the  nitrogenous  principles  have  no  close  quantitative 
relations  to  the  non-nitrogenous  bodies  (carbhydrates 
and  fats). 

The  quantities  of  albuminoids  gained  during  each 
period  being  represented  by  10,  the  amounts  of  carbhy- 
drates, etc.,  are  seen  from  the  subjoined  ratios  : 

PERIODS. 

Ratio  in 
I.  II  &  III.          IV.  V.      Ripe  Plant. 

Arendt 10:34         10:114         10:28       10  :     25       10:66 

Bretschneider..lO  :  30        10  :    50        10  :  46       10  :  120       10  :  51 

5.  The  Ash-ingredients  of  the  oat  are  absorbed  through- 
out its  entire  growth,  but  in  regularly  diminishing  quan- 
tity. The  gain  during  the  1st  Period  being  taken  at  10, 
that  in  the  2d  Period  is  9,  in  the  3d,  8,  in  the  4th,  5£, 
in  the  5th,  2  nearly. 

The  ratios  of  gain  in  ash -ingredients  to  that  in  entire 
dry  substance,  are  as  follows,  ash-ingredients  being 
assumed  as  1,  in  the  successive  periods  : 


236  HOW  CROPS  GEOW. 

1  :  12},       1  :  27,       1  :  16,       1  :  23,       1  :  19. 

Accordingly,  the  absorption  of  ash-ingredients  is  not 
proportional  to  the  growth  of  the  plant,  but  is  to  some 
degree  accidental,  and  independent  of  the  wants  of 
vegetation. 

Recapitulation. — Assuming  the  quantity  of  each  proxi- 
mate element  in  the  ripe  plant  as  100,  it  contained  at 
the  end  of  the  several  periods  the  following  amounts 
(per  cent) : 

Fiber.  Fat.  Carbhydrates.*  Albuminoids.  A»h. 

1.  Period,           18           20                15                     27  29 

II.        "                   81            50                 47                       45  55 

III.  "                100           85                70                     57  79 

IV.  "                  100  100                 92                      90  95 
V.        "                 100  100               100                     100  100 

Taking  the  total  gain  as  100,  the  gain  during  each 
period  was  accordingly  as  follows  (per  cent) : 

Fiber.      Fat.  Carbhydrates.*  Albuminoids.  Ash. 

I.  Period,          18          20              15                   27  29 

II.        "                   63           30                 32                      18  26 

HI.        "                   19           35                 23                      12  24 

IV.        "                    0           15                22                     33  16 

V.        "                    00                  8                     10  5 

100          100  100  100  "lOO 

6. — As  regards  the  individual  ingredients  of  the  ask, 
the  plant  contained  at  the  end  of  each  period  the  follow- 
ing amounts, — the  total  quantity  in  the  ripe  plant  being 
taken  at  100.  Corresponding  results  from  Bretschneider 
enclosed  in  (  )  are  given  for  comparison: 

Sulphuric  Phosphoric 

Silica.         Oxide  Oxide            Lime.  Magnesia.  Potash. 

Per  cent.  Per  cent.  Per  cent.  Per  cent.  Per  cent.  Per  cent. 

L  Period,     18    (  22)    20    (42)  23    (  23)    30    (31)  24    (  31)  39    (  42) 

II.        «           41|(5       62  J  (44)  42}              58»(83)  42.  70. 

III.  "     70  J     52'  73*      79)    '  58  J  91  ' 

IV.  ««     93  (72)  90  (  39)  91  (74)  99  (  74)  84  (  77)  100  (100) 
V.    "    100  (100)  100  (100)  100  (100)  100  (100)  100  (100)  100  (95*) 

The  gain  (or  loss,  indicated  by  the  minus  sign  — )  in 
these  ash-ingredients  during  each  period  is  given  below: 

*  Exclusive  of  Fiber. 


COMPOSITION   IN  SUCCESSIVE   STAGES.  237 


Silica. 

Sulphuric 
Oxide. 

Phosphoric 
Oxide. 

Lime. 

Magnesia. 

Potash. 

Per  cent 

.  Per  cent. 

Per  cent 

.  Per  cent. 

Per  cent. 

Per  cent. 

I. 
II. 
III. 

Period,  18    (  22) 

"          23\(35) 
29) 

20 
32 
0 

(42) 
j(  2) 

23 
19 
31 

(23) 
|(40) 

30 

(31  ) 

24 

18 
16 

(31) 
[(42) 

39 
31) 
21) 

(42) 
|(47) 

IV. 
V. 

"          23    (  15) 

7    (  28) 

38 
10 

(-5*) 
(56) 

18 
9 

(10) 
(27) 

20 
1 

(-»*) 
(17) 

26 
16 

(4) 
(23) 

9 
0 

(11  ) 

(-5*) 

100    (100) 

100 

(100) 

100 

(100) 

100 

(100) 

100 

(100) 

100 

(100) 

These  two  independent  investigations  could  hardly 
give  all  the  discordant  results  observed  on  comparing 
the  above  figures,  as  the  simple  consequence  of  the 
unlike  mode  of  conducting  them.  We  observe,  for 
example,  that  in  the  last  period  Arendt's  plants  gathered 
less  silica  than  in  any  other — only  7  per  cent  of  the 
whole.  On  the  other  hand,  Bretschneider's  crop  gained 
more  silica  in  this  than  in  any  other  single  period,  viz. : 
28  per  cent.  A  similar  statement  is  true  of  phosphoric 
oxide,  f  It  is  obvious  that  Bretschneider's  crop  was  tak- 
ing up  fixed  matters  much  more  vigorously  in  its  last 
stages  of  growth  than  were  Arendt's  plants.  As  to 
potash,  we  observe  that  its  accumulation  ceased  in  the 
4th  Period  in  both  cases. 

C. — Translocation  of  Substances  in  the  Plant. 
—The  transfer  of  certain  matters  from  one  part  of  the 
plant  to  another  during  its  growth  is  revealed  by  the 
analyses  of  Arendt,  and  since  such  changes  are  of  inter- 
est from  a  physiological  point  of  view,  we  may  recount 
them  here  briefly. 

It  has  been  mentioned  already  that  the  growth  of  the 
stem,  leaves,  and  ear  of  the  oat  plant  in  its  later  stages 
probably  takes  place  to  a  great  degree  at  the  expense  of 
the  roots.  It  is  also  probable  that  a  transfer  of  carbhy- 


*In  these  instances  Bretschneider's  later  crops  appear  to  contain  less 
sulphuric  oxide,  lime  and  potash, than  the  earlier.  Thisresult  maybe 
due  to  the  washing  of  the  crop  by  rains,  but  is  probably  caused  by 
unequal  development  of  the  several  plots. 

t  Phosphoric  oxide  is  the  "phosphoric  acid,"  P2OS,  of  older  and  to  a 
great  degree  of  current  usage.  See  p.  163. 


238  HOW  CROPS  GROW. 

drates,  and  certain  that  one  of  albuminoids,  goes  on  from 
the  leaves  through  the  stem  into  the  ear. 

Silica,  appears  not  to  be  subject  to  any  change  of  posi- 
tion after  it  has  once  been  fixed  by  the  plant.  Chlorine 
likewise  reveals  no  noticeable  mobility. 

On  the  other  hand,  phosphoric  oxide  passes  rapidly  from 
the  leaves  and  stem  towards  or  into  the  fruit  in  the  ear- 
lier as  well  as  in  the  later  stages  of  growth,  as  shown  by 
the  following  figures : 

One  thousand  plants  contained  in  the  various  periods 
quantities  (grams)  of  phosphoric  oxide  as  follows  : 

1st  2d  3d               4th  6th 

Period.  Period.  Period.  Period.  Period. 

3  lower  joints  of  stem,  0.47  0.20  0.21            0.20  0.19 

2  middle    "               "  0.39  1.14            0.46  0.18 
Upper  joint              "  0.66  1.73            0.31  0.39 

3  lower  leaves         "       1.05  0.70  0.69           0.51  0.35 
2  upper  leaves         "       1.75  1.67  1.18           0.74  0.59 
Ear,  2.36  5.36  10.67  12.52 

Observe  that  these  absolute  quantities  diminish  in  the 
stem  and  leaves  after  the  1st  or  3d  Period  in  all  cases, 
and  increase  very  rapidly  in  the  ear. 

Arendt  found  that  sulphuric  oxide  existed  to  a  much 
greater  degree  in  the  leaves  than  in  the  stem  through- 
out the  entire  growth  of  the  oat  plant,  and  that,  after 
blossoming,  the  lower  stem  no  longer  contained  sulphur 
in  the  form  of  sulphates  at  all,  though  its  total  in  the 
plant  considerably  increased.  It  is  almost  certain,  then, 
that  sulphuric  oxide  originates,  either  partially  or  wholly, 
by  oxidation  of  sulphur  or  some  sulphurized  compound, 
in  the  upper  organs  of  the  oat. 

Magnesium  is  translated  from  the  lower  stem  into  the 
upper  organs,  and  in  the  fruit,  especially,  it  constantly 
increases  in  quantity. 

There  is  no  evidence  that  Calcium  moves  upward  in 
the  plant.  On  the  contrary,  Arendt's  analyses  go  to 
show  that  in  the  ear,  during  the  last  period  of  growth,  it 


COMPOSITION  IK  SUCCESSIVE  STAGES.  239 

diminishes  in  quantity,  being,  perhaps,  replaced  by 
magnesium. 

As  to  potassium,  no  transfer  is  fairly  indicated,  except 
from  the  ears.  These  contained  at  blossoming  (Period 
III)  a  maximum  of  potassium,  During  their  subsequent 
growth  the  amount  of  this  element  diminished,  being 
probably  displaced  by  magnesium. 

The  data  furnished  by  Arendt's  analyses,  while  they 
indicate  a  transfer  of  matters  in  the  cases  just  named, 
and  in  most  of  them  with  great  certainty,  do  not  and 
cannot  from  their  nature  disprove  the  fact  of  other  simi- 
lar changes,  and  cannot  fix  the  real  limits  of  the  move- 
ments which  they  point  out. 


DIVISION  II. 

THE    STRUCTURE    OF    THE    PLANT    AND 
OFFICES    OF   ITS    ORGANS. 

CHAPTER  I. 
GENERALITIES. 

We  have  given  a  brief  description  of  those  elements 
and  compounds  which  constitute  the  plant  in  a  chemical 
sense.  They  are  the  materials — the  stones  and  timbers, 
so  to  speak — out  of  which  the  vegetable  edifice  is  built. 
It  is  important,  in  the  next  place,,  to  learn  how  these 
building  materials  are  put  together,  what  positions  they 
occupy,  what  purposes  they  serve,  and  on  what  plan 
the  edifice  is  constructed. 

It  is  impossible  for  the  builder  to  do  his  work  until  he 
has  mastered  the  plans  and  specifications  of  the  archi- 
tect. So  it  is  hardly  possible  for  the  farmer  with  cer- 
tainty to  contribute  in  any  great,  especially  in  any  new, 
degree,  to  the  upbuilding  of  the  plant,  unless  he  is 
acquainted  with  the  mode  of  its  structure  and  the  ele- 
ments that  form  it.  It  is  the  happy  province  of  science 
to  add  to  the  vague  and  general  information  which  the 
observation  and  experience  of  generations  have  taught, 
a  more  definite  and  particular  knowledge, — a  knowledge 
acquired  by  study  purposely  and  carefully  directed  to 
special  ends. 

An  acquaintance  with  the  parts  and  structure  of  the 
plant  is  indispensable  for  understanding  the  mode  by 
which  it  derives  its  food  from  external  sources,  while  the 
16  241 


242  HOW  CEOPS  GROW. 

ingenious  methods  of  propagation  practiced  in  fruit-  and 
flower-culture  are  only  intelligible  by  the  help  of  this 
knowledge. 

ORGANISM  OF  THE  PLANT. — We  have  at  the  outset 
spoken  of  organic  matter,  of  organs  and  organization. 
It  is  in  the  world  of  life  that  these  terms  have  their  fit- 
test application.  The  vegetable  and  animal  consist  of 
numerous  parts,  differing  greatly  from  each  other,  but 
each  essential  to  the  whole.  The  root,  stem,  leaf,  flower 
and  seed  are  each  instruments  or  organs  whose  co-oper- 
ation is  needful  to  the  perfection  of  the  plant.  The 
plant  (or  animal)  being  thus  an  assemblage  of  organs,  is 
called  an  Organism;  it  is  an  Organized  or  Organic 
Structure.  The  atmosphere,  the  waters,  the  rocks  and 
soils  of  the  earth,  do  not  possess  distinct  co-operating 
parts  ;  they  are  Inorganic  matter. 

In  inorganic  nature,  chemical  affinity  rules  over  the 
transformations  of  matter.  A  plant  or  animal  that  is 
dead,  under  ordinary  circumstances,  soon  loses  its  form 
and  characters  ;  it  is  gradually  consumed,  and,  at  the  ex- 
pense of  atmospheric  oxygen,  is  virtually  burned  up  to 
air  and  ashes. 

In  the  organic  world  a  something,  which  we  call 
Vitality,  resists  and  overcomes  or  modifies  the  affinities 
of  oxygen,  and  insures  the  existence  of  a  continuous  and 
perpetual  succession  of  living  forms. 

An  Organism  or  Organized  Structure  is  characterized 
and  distinguished  from  inorganic  matter  by  two  par- 
ticulars : 

1.  It  builds  up  and  increases  its  own  mass  by  appro- 
priating external  matter.     It  absorbs  and  assimilates 
food.     It  grows  by  the  enlargement  of  all  its  parts. 

2.  It  reproduces  itself.     It  develops  from  a  germ,  and 
in  turn  gives  origin  to  new  germs. 

ULTIMATE  AND  COMPLEX  ORGANS. — In  our  account 
of  the  Structure  of  the  Plant  we  shall  first  consider  the 


ELEMENTS  OF  ORGANIZED  STRUCTURE.  243 

elements  of  that  structure  —  the  Cells  —  which  cannot  be 
divided  or  wounded  without  extinguishing  their  life, 
and  by  whose  expansion  or  multiplication  all  growth 
takes  place.  Then  will  follow  an  account  of  the  com- 
plex parts  of  the  plant  —  its  Organs  —  which  are  built  up 
by  the  juxtaposition  of  numerous  cells.  Of  these  we 
have  one  class,  viz.,  the  Eoots,  Stems  and  Leaves,  whose 
office  is  to  sustain  and  nourish  the  Individual  Plant. 
These  may  be  distinguished  as  the  Vegetative  Organs. 
The  other  class,  comprising  the  Flower  and  Fruit,  are 
not  essential  to  the  existence  of  the  individual,  but  their 
function  is  to  maintain  the  Race.  They  are  the  Repro- 
ductive Organs. 

CHAPTER   II. 
PRIMARY   ELEMENTS   OF   ORGANIZED   STRUCTURE. 


THE  VEGETABLE   CELL. 

One  of  the  most  interesting  discoveries  that  the  micro- 
scope has  revealed,  is  that  all  organized  matter  originates 
in  the  form  of  minute  vesicles  or  cells.  If  we  examine 
by  the  microscope  a  seed  or  an  egg,  we  find  nothing  but 
a  cell-structure  —  a  mass  of  rounded  or  many-sided  bags 
lying  closely  together,  and  more  or  less  filled  with  solid 
or  liquid  matters.  From  these  cells,  then,  comes  the 
frame  or  structure  of  the  plant  or  of  the  animal.  In  the 
process  of  maturing,  the  original  vesicles  are  vastly  mul- 
tiplied and  often  greatly  modified  in  shape  and  appear- 
ance, to  suit  various  purposes  ;  but  still  it  is  always  easy, 
especially  in  the  plant,  to  find  cells  of  the  same  essential 
characters  as  those  occurring  in  the  seed. 


244  HOW  CROPS  GROW. 

Cellular  Plants. — In  the  simpler  forms  or  lower 
orders  *  of  vegetation,  we  find  plants  which,  throughout 
all  the  stages  of  their  life,  consist  entirely  of  similar 
cells,  and  indeed  many  are  known  which  are  but  a  single 
cell.  The  phenomenon  of  red  snow,  frequently  observed 
in  Alpine  and  Arctic  regions,  is  due  to  a  microscopic 
one-celled  plant  which  propagates  with  great  rapidity, 
and  gives  its  color  to  the  surface  of  the  snow.  In  the 
chemist's  laboratory  it  is  often  observed  that  in  the  clear- 
est solutions  of  salts,  like  the  sulphates  of  sodium  and 
magnesium,  a  flocculent  mold,  sometimes  red,  some- 
times green,  most  often  white,  is  formed,  which,  under 
the  microscope,  is  seen  to  be  a  vegetation  consisting  of 
single  cells.  Brewers'  yeast,  Fig.  27,  is  nothing  more 
than  a  mass  of  one  or  few-celled  plants. 

In  sea-weeds,  mushrooms,  the  molds  that  grow  on 
damp  walls,  or  upon  bread,  cheese,  etc.,  and  in  the 
blights  which  infest  many  of  the  farmer's  crops,  we  have 
examples  of  plants  formed  exclusively  of  cells. 


All  the  plants  of  higher  orders  we  find  likewise  to 
consist  chiefly  of  globular  or  angular  cells.  All  the 
growing  parts  especially,  as  the  tips  of  the  roots,  the 
leaves,  flowers  and  fruit,  are,  for  the  most  part,  aggrega- 
tions of  such  minute  vesicles. 

If  we  examine  the  pulp  of  fruits,  as  that  of  a  ripe 

*Viz. :   the  Cryptogams,   including  Molds  and   Mushrooms  (Fungi\ 
Mosses,  Ferns,  Sea- Weeds  (Algae)  and  Bacteria  (Schizomycetes). 


ELEMENTS  OF  OBGANIZED  STBUCTUBE.  245 

apple  or  tomato,  we  are  able,  by  means  of  a  low  magni- 
fier, to  distinguish  the  cells  of  which  it  almost  entirely 
consists.  Fig.  28  represents  a  bit  of  the  flesh  of  a  ripe 
pippin,  magnified  50  diameters.  The  cells  mostly  cohere 
together,  but  readily  admit  of  separation. 

Structure  of  the  Cell. — By  the  aid  of  the  micro- 
scope it  is  possible  to  learn  something  with  regard  to  the 
internal  structure  of  the  cell  itself.  Fig.  29  exhibits  the 
appearance  of  a  cell  from  the  flesh  of  the  Artichoke 
(Helianthus),  magnified  230  diameters ;  externally  the 
membrane,  or  wall  of  the  cell,  is  seen  in  section.  This 
membrane  is  filled  and  distended  by  a 
transparent  liquid,  the  sap  or  free  water 
of  vegetation.  Within  the  cell  is  ob- 
served  a  round  body,  b,  which  is  called 
the  nucleus,  and  upon  this  is  seen  a 
smaller  nucleolus,  c.  Lining  the  inte- 
rior of  the  cell-membrane  and  connected 
with  the  nucleus,  is  a  yellowish,  turbid, 
semi-fluid  substance  of  mucilaginous 
consistence,  a,  which  is  designated  the  protoplasm,  or 
formative  layer.  This,  when  more  highly  magnified,  is 
found  to  contain  a  vast  number  of  excessively  minute 
granules. 

By  the  aid  of  chemistry  the  microscopist  is  able  to  dis- 
sect these  cells,  which  are  hardly  perceptible  to  the 
unassisted  eye,  and  ascertain  to  a  good  degree  how  they 
are  constituted.  On  moistening  them  with  solution  of 
iodine,  and  afterward  with  sulphuric  acid,  the  outer 
membrane — the  cell-wall — shortly  becomes  of  a  fine  blue 
color.  It  is  accordingly  cellulose,  the  only  vegetable 
substance  yet  known  which  is  made  blue  by  iodine  after, 
and  only  after,  the  action  of  sulphuric  acid.  At  the 
same  time  we  observe  that  the  interior,  half -liquid,  pro- 
toplasm, coagulates  and  shrinks  together, — separates, 
therefore,  from  the  cell-wall,  and,  including  with  it  the 


246  HOW  CROPS  GEOW. 

nucleus  and  the  smaller  granules,  lies  in  the  center  of 
the  cell  like  a  collapsed  bladder.  It  also  assumes  a  deep 
yellow  or  brown  color.  If  we  moisten  one  of  these  cells 
with  nitric  acid,  the  cell- wall  is  not  affected,  but  the 
liquid  penetrates  it,  coagulates  the  inner  membrane,  and 
colors  it  yellow.  In  the  same  way  this  membrane  is 
tinged  violet-blue  by  hydrochloric  acid.  These  reactions 
leave  no  room  to  doubt  that  the  slimy  inner  lining  of  the 
cell  or  protoplasm  contains  abundance  of  albuminoids. 
The  protoplasm  is  not  miscible  with  water  and  main- 
tains itself  distinct  from  the  cell-sap.  In  young  cells  it 
is  constantly  in  motion,  the  granules  suspended  in  it  cir- 
culating as  in  a  liquid  current. 

If  we  examine  the  cells  of  any  other  plant  we  find 
almost  invariably  the  same  structure  as  above  described, 
provided  the  cells  are  young,  i.  e.,  belong  to  growing 
parts.  In  some  cases  isolated  cells  consist  only  of  proto- 
plasm and  nucleus,  being  destitute  of  cell-walls  during 
a  portion  or  the  whole  of  their  existence. 

In  studying  many  of  the  maturer  parts  of  plants,  viz., 
such  as  have  ceased  to  enlarge,  as  the  full-sized  leaf,  the 
perfectly  formed  wood,  etc.,  we  find  the  cells  do  not  cor- 
respond to  the  description  just  given.  In  external  shape, 
thickness,  and  appearance  of  the  cell-wall,  and  especially 
in  the  character  of  the  contents,  there  is  indefinite  va- 
riety. But  this  is  the  result  of  change  in  the  original 
cells,  which,  so  far  as  our  observations  extend,  are  always, 
at  first,  formed  closely  on  the  pattern  that  has  been  de- 
scribed. 

Vegetable  Tissue. — It  does  not,  however,  usually 
happen  that  the  individual  cells  of  the  higher  orders  of 
plants  admit  of  being  obtained  separately.  They  are 
attached  together  more  or  less  firmly  by  their  outer  sur- 
faces, so  as  to  form  a  coherent  mass  of  cells — a  tissue,  as 
it  is  termed.  In  the  accompanying  cut,  Fig.  30,  is  shown 
a  highly-magnified  view  of  a  portion  of  a  very  thin  slice 


ELEMENTS  OF  ORGANIZED   STRUCTURE.  247 

across  a  young  cabbage-stalk.  It  exhibits  the  outline  of 
the  irregular  empty  cells,  the  walls  of  which  are,  for  the 
most  part,  externally  united  and  appear  as  one,  a.  At 
the  points  indicated  by  5,  air-filled  cavities  between  the 
cells  are  seen,  called  intercellular  spaces.  A  slice  across 
the  potato-tuber  (see  Fig,  52,  p.  300)  has  a  similar  ap- 
pearance, except  that  the  cells  are  filled  with  starch,  and 

it  would  be  scarcely  pos- 
sible to  dissect  them  apart; 
but  when  a  potato  is  boiled 
the  starch  -  grains  swell, 
and  the  cells,  in  conse- 
'quence,  separate  from  each 
other,  a  practical  result  of 
which  is  to  make  the  po- 
tato mealy.  A  thin  slice 
of  vegetable  ivory  (the  seed 
ofPhytelephas  macro- 
Fig,  so.  carpa)  under  the  micro- 
scope, dry  or  moistened  with  water,  presents  no  evident 
trace  of  cell-structure  ;  however,  upon  soaking  in  sul- 
phuric acid,  the  mass  softens  and  swells,  and  the  indi- 
vidual cells  are  revealed,  their  surfaces  separating  in 
six-sided  outlines. 

Form  of  Cells. — In  the  soft,  succulent  parts  of 
plants,  the  cells  lie  loosely  together,  often  with  consider- 
able intercellular  spaces,  and  have  mostly  a  rounded  out- 
line. In  denser  tissues,  the  cells  are  crowded  together 
in  the  least  possible  space,  and  hence  often  appear  six- 
sided  when  seen  in  cross-section,  or  twelve-sided  if  viewed 
entire.  A  piece  of  honey-comb  is  an  excellent  illustra- 
tion of  the  appearance  of  many  forms  of  vegetable  cell- 
tissue. 

The  pulp  of  an  orange  is  the  most  evident  example  of 
cell-tissue.  The  individual  cells  of  the  ripe  orange  may 
be  easily  separated  from  each  other.  Being  mature  and 


248 


HOW  CROPS  GROW. 


incapable  of  further  growth,  they  possess  neither  proto- 
plasm nor  nucleus,  but  are  filled  with  a  sap  or  juice  con- 
taining citric  acid,  sugar  and  albuminoids. 
In  the  pith  of  the  rush,  star-shaped  cells  are  found. 
In  common  mold  the  cells  are  long  and 
| thread-like.     In  the  so-called  frog-spittle 
(algce)  they  are  cylindrical  and  attached 
end  to  end.     In  the  bark  of  many  trees, 
in  the  stems  and  leaves  of  grasses,  they 
are  square  or  rectangular. 

Cotton-fiber,  flax,  and  hemp  consist  of 
long  and  slender  cells,  Fig.  31.  Wood  is 
mostly  made  up  of  elongated  cells,  tapered 
at  the  ends  and  adhering  together  by 
their  sides.  See  also  Fig.  49,  c,  h,  p.  292. 

Each  cotton-fiber  is  a  single  cell  which  forms  an 
external  appendage  to  the  seed-vessel  of  the  cotton 
^  plant.  Wlieii  it  has  lost  its  sap  and  become  air-dry, 
its  sides  collapse  and  it  resembles  a  twisted  strap. 
\A,  in  Fig.  31,  exhibits  a  portion  of  a  cotton-fiber 
highly  magnified.  The  flax-liber,  from  the  inner 
bark  of  the  flax-stem,  b,  Fig.  31,  is  a  tube  of  thicker 
walls  and  smaller  bore  than  the  cotton-fiber,  and. 
hence  is  more  durable  than  cotton.  It  is  very  flexi- 
ble, and  even  when  crushed  or  bent  short  retains  much  of  its  original 
tenacity.  Hemp-fiber  closely  resembles  flax-fiber  in  appearance. 

Thickening  of  the  Cell-Membrane. — The  growth  of  the  cell,  which, 
When  young,  has  a  very  delicate  outer 
membrane,  often  results  in  the  thick- 
ening of  its  walls  by  the  interior  dep- 
osition of  cellulose  and  woody  mat- 
ters. This  thickening  may  take  place  vJ-| 
regularly  and  uniformly,  or  interrupt- 
edly. The  flax-fiber,  b,  Fig.  31,  is  an  ex- 
ample of  nearly  uniform  thickening. 
The  irregular  deposition  of  cellulose  is 
shown  in  Fig.  32,  which  exhibits  a  sec- 
tion from  the  seeds  (cotyledons)  of  the 
common  nasturtium  ( Tropveolum 
majus).  The  original  membrane  is  coated  interiorly  with  several  dis- 
tinct and  successively-formed  linings,  which  are  not  continuous,  but 
are  irregularly  developed.  Seen  in  section,  the  thickening  has  a  waved 
outline,  and,  at  points,  the  original  coil-membrane  is  bare.  Were  these 
cells  viewed  entire,  we  should  see  at  these  points,  on  the  exterior  of 
the  cell,  dots  or  circles  appearing  like  orifices,  but  being  simply  the 


Fig.  31. 


Fig.  32. 


ELEMENTS  OF  ORGANIZED  STBUCTDBE.  249 

ttnthickened  portions  of  the  cell-wall.    The  cells  in  fig.  32  exhibit  each 
a  central  nucleus  surrounded  by  grains  of  aleurone. 

Cell  Contents. — Besides  the  protoplasm  and  nucleus, 
the  cell  usually  contains  a  variety  of  bodies,  which  have 
been,  indeed,  noticed  already  as  ingredients  of  the  plant, 
but  which  may  be  here  recapitulated.  Many  cells  arc 
altogether  empty,  and  consist  of  nothing  but  the  cell- 
wall.  Such  are  found  in  the  bark  or  epidermis  of  most 
plants,  and  often  in  the  pith,  and  although  they  remain 
connected  with  the  actually  living  parts,  they  have  no 
longer  any  proper  life  in  themselves. 

All  living  or  active  cells  are  distended  with  liquid. 
This  consists  of  water,  which  holds  in  solution  gum,  dex- 
trin, inulin,  the  sugars,  albuminoids,  organic  acids,  and 
other  vegetable  principles,  together  with  various  salts, 
both  of  organic  and  mineral  acids,  and  constitutes  the 
sap  of  the  plant.  In  oil-plants,  droplets  of  oil  occupy 
certain  cells,  Fig.  17,  p.  83;  while  in  numerous  kinds  of 
vegetation  colored  and  milky  juices  are  found  in  certain 
spaces  or  channels  between  the  cells. 

The  water  of  the  cell  comes  from  the  soil,  or  in  some 
cases  from  the  air.  The  matters,  which  are  dissolved  in 
the  sap  of  the  plant,  together  with  the  semi-solid  proto- 
plasm, undergo  transformations  resulting  in  the  produc- 
tion of  various  solid  substances.  By  observing  the  sev- 
eral parts  of  a  plant  at  the  successive  stages  of  its  devel- 
opment, under  the  microscope,  we  are  able  to  trace 
within  the  cells  the  formation  and  growth  of  starch- 
grains,  of  granular  or  crystalline  bodies  consisting  chiefly 
of  albuminoids,  and  of  the  various  matters  which  give 
color  to  leaves  and  flowers. 

The  circumstances  under  which  a  cell  develops  deter- 
mine the  character  of  its  contents.  The  outer  cells  of 
the  potato-tuber  are  incrusted  with  corky  matter,  the 
inner  ones  are  for  the  most  part  filled  with  starch. 

In  oats,  wheat,  and  other  cereals,  we  find,  just  within 


250  HOW  CHOPS  GEOW. 

the  skin  or  epidermis  of  the  grain,  a  few  layers  of  cells 
that  contain  scarcely  anything  but  albuminoids,  with  a 
little  fat ;  while  the  interior  cells  are  chiefly  filled  with 
starch.  Fig.  18,  p.  110. 

Transformations  in  Cell  Contents. — The  same 
cell  may  exhibit  a  great  variety  of  aspect  and  contents  at 
different  periods  of  growth.  This  is  especially  to  be 
observed  in  the  seed  while  developing  on  the  mother 
plant.  Hartig  has  traced  these  changes  in  numerous 
plants  under  the  microscope.  According  to  this  ob- 
server, the  cell-contents  of  the  seed  (cotyledons)  of  the 
common  nasturtium  (TropcBolum  majus)  run  through 
the  following  metamorphoses.  Up  to  a  certain  stage  in 
its  development  the  interior  of  the  cells  are  nearly  devoid 
of  recognizable  solid  matters,  other  than  the  nucleus  and 
the  adhering  protoplasm.  Shortly,  as  the  growth  of  the 
seed  advances,  green  grains  of  chlorophyll  make  their 
appearance  upon  the  nucleus,  completely  covering  it 
from  view.  At  a  later  stage,  these  grains,  which  have 
enlarged  and  multiplied,  are  seen  to  have  mostly  become 
detached  from  the  nucleus,  and  lie  near  to  and  in  contact 
with  the  cell- wall.  Again,  in  a  short  time  the  grains 
lose  their  green  color  and  assume,  both  as  regards  appear- 
ance and  deportment  with  iodine,  all  the  characters  of 
starch.  Subsequently,  as  the  seed  hardens  and  becomes 
firmer  in  its  tissues,  the  microscope  shows  that  the 
starch-grains,  which  were  situated  near  the  cell-wall, 
have  vanished,  while  the  cell-wall  itself  has  thickened 
inwardly — the  starch  having  been  converted  into  cellu- 
lose or  bodies  of  similar  properties.  Again,  later,  the  nu- 
cleus, about  which,  in  the  meantime,  more  starch-grains 
have  been  formed,  undergoes  a  change  and  disappears  ; 
then  the  starch-grains,  some  of  which  have  enlarged  while 
others  have  vanished,  are  found  to  be  imbedded  in  a  pasty 
matter,  which  has  the  reactions  of  an  albuminoid.  From 
this  time  on,  the  starch-grains  are  gradually  converted 


ELEMENTS  OF  ORGANIZED  STKUCTtJBE. 


251 


from  their  surfaces  inwardly  into  smaller  grains  of  aleu- 
rone,  which,  finally,  when  the  seed  is  mature,  completely 
occupy  the  cells. 

In  the  sprouting  of  the  seed  similar  changes  occur,  but 
in  reversed  order.  The  nucleus  reappears,  the  aleurone 
dissolves,  and  even  the  cellulose*  stratified  upon  the  inte- 
rior of  the  cell  (Fig.  32)  wastes  away  and  is  converted  into 
soluble  food  (sugar  ?)  for  the  seedling  plant. 


Fig.  38. 

The  Dimensions  of  Vegetable  Cells  are  very  vari- 
ous. A  creeping  marine  plant  is  known — the  Caulerpa, 
prolifera  (Fig.  33) — which  consists  of  a  single  cell,  though 
it  is  often  a  foot  in  length,  and  is  branched  with  what 
have  the  appearance  of  leaves  and  roots.  The  pulp  of 


*  Or  more  probably  metarabin,  paragalaetin,  xylin,  or  the  like  insol- 
uble substances,  which  as  yet  have  been  but  imperfectly  distinguished 
from  cellulose  iu  the  thickened  cell-walls. 


252 


HOW  CROPS  GROW. 


the  orange  consists  of  cells  which  are  one-quarter  of  an 
inch  or  more  in  diameter.  The  fiber  of  cotton  is  a  single 
cell,  commonly  from  one  to  two  inches  long.  In  most 
cases,  however,  the  cells  of  plants  are  so  small  as  to  re- 
quire a  powerful  microscope  to  distinguish  them, — are, 
in  fact,  no  more  than  j^^  to  5£<y  of  an  inch  in  diame- 
ter. The  spores  of  Fungi  are  still  smaller.  The  germs 
of  many  bacteria  are  so  minute  as  to  be  undiscoverable 
by  the  highest  powers  of  the  microscope. 

Growth. — The  growth  of  a  plant  is  nothing  more 
than  the  aggregate  result  of  the  enlargement  and  multi- 
plication of  the  cells  which  compose  it.  In  most  cases 
the  cells  attain  their  full  size  in  a  short  time.  The  con- 
tinuous growth  of  plants  depends,  then,  chiefly  on  the 
constant  and  rapid  formation  of  new  cells. 

Cell-multiplication. — The    young   and    active  cell 


Fig  34.  Fig.  35. 

always  contains  a  nucleus  (Fig.  34,  5).  Such  a  cell  may 
produce  a  new  cell  by  division.  In  this  process  the  nu. 
cleus,  from  which  all  cell-growth  appears  to  originate,  is 
observed  to  resolve  itself  into  two  parts,  then  the  proto- 
plasm, a,  begins  to  contract  or  infold  across  the  cell  in  a 
line  corresponding  with  the  division  of  the  nucleus,  until 
the  opposite  infolded  edges  meet, — like  the  skin  of  a  sau- 
sage where  a  string  is  tightly  tied  around  it, — thus  sepa- 
rating the  two  nuclei  and  inclosing  each  within  its  new 
cell,  which  is  completed  by  a  further  external  growth  of 
cellulose, 


ELEMENTS   OF   ORGANIZED    STEUCIUBE.  253 

In  one-celled  plants,  like  yeast  (Fig.  35),  the  new  cells 
thus  formed,  bud  out  from  the  side  of  the  parent-cell, 
and  before  they  obtain  full  size  become  entirely  detached 
from  it,  or,  as  in  higher  plants,  the  new  cells  remain  ad- 
hering to  the  old,  forming  a  tissue. 

In  free  cell-formation  nuclei  are  observed  to  develop  in 
the  protoplasm  of  a  parent  cell,  which  enlarge,  surround 
themselves  with  their  own  protoplasm  and  cell-membrane, 
and  by  the  resorption  or  death  of  the  parent  cell  become 
independent. 

The  rapidity  with  which  the  vegetable  cells  may  mul- 
tiply and  grow  is  illustrated  by  many  familiar  facts. 
The  most  striking  cases  of  quick  growth  are  met  with  in 
the  mushroom  family.  Many  will  recollect  having  seen, 
on  the  morning  of  a  June  day,  huge  puff-balls,  some  as 
large  as  a  peck  measure,  on  the  surface  of  a  moist 
meadow,  where  the  day  before  nothing  of  the  kind  was 
noticed.  In  such  sudden  growth  it  has  been  estimated 
that  the  cells  are  produced  at  the  rate  of  three  or  four 
hundred  millions  per  hour. 

Permeability  of  Cells  to  Liquids. — Although  the 
highest  magnifying  power  that  can  be  brought  to  bear 
upon  the  membranes  of  the  vegetable  cell  fails  to  reveal 
any  apertures  in  them, — they  being,  so  far  as  the  best- 
assisted  vision  is  concerned,  completely  continuous  and 
imperf orate, — they  are  nevertheless  readily  permeable  to 
liquids.  This  fact  may  be  shown  by  placing  a  delicate 
slice  from  a  potato  tuber,  immersed  in  water,  under  the 
microscope,  and  then  bringing  a  drop  of  solution  of 
iodine  in  contact  with  it.  Instantly  this  reagent  pene- 
trates the  walls  of  the  unbroken  cells  without  perceptibly 
affecting  their  appearance,  and,  being  absorbed  by  the 
starch-grains,  at  once  colors  them  intensely  purplish- 
blue.  The  particles  of  which  the  cell-walls  and  their 
contents  are  composed  must  be  separated  from  each 
other  by  distances  greater  than  the  diameter  of  the  .par- 


254  HOW   CEOPS   GROW. 

tides  of  water  or  of  other  liquid  matters  which  thus  per- 
meate the  cells. 


THE    VEGETABLE    TISSUES. 

As  already  stated,  the  cells  of  the  higher  kinds  of 
plants  are  united  together  more  or  less  firmly,  and  thus 
constitute  what  are  known  as  VEGETABLE  TISSUES.  Of 
these,  a  large  number  have  been  distinguished  by  vege- 
table anatomists,  the  distinctions  being  based  either  ou 
peculiarities  of  form  or  of  function.  For  our  purposes 
it  will  be  necessary  to  define  but  a  few  varieties,  viz.  : 
Cellular  Tissue,  Wood-  Tissue,  Bast-Tissue  and  Vas- 
cular Tissue. 

Cellular  Tissue,  or  Parenchyma,  is  the  simplest  of 
all,  being  a  mere  aggregation  of  globular  or  polyhedral 
cells  whose  walls  are  in  close  adhesion,  and  whose  juices 
commingle  more  or  less  in  virtue  of  this  connection. 
Cellular  tissue  is  the  groundwork  of  all  vegetable  struc- 
ture, being  the  only  form  of  tissue  in  the  simpler  kinds 
of  plants,  and  that  out  of  which  all  the  other  tissues  are 
developed. 

Prosenchyma  is  a  name  applied  to  all  tissues  composed 
of  elongated  cells,  like  those  of  wood  and  bast.  Paren- 
chyma and  prosenchyma  insensibly  shade  into  each 
other. 

Wood-Tissue,  in  its  simplest  form,  consists  of 
cells  that  are  several  or  many  times  as  long  as  they  are 
broad,  and  that  taper  at  each  end  to  a  point.  These 
spindle-shaped  cells  cohere  firmly  together  by  their  sides, 
and  "break  joints  "by  overlapping  each  other,  in  this 
way  forming  the  tough  fibers  of  wood.  Wood-cells  are 
often  more  or  less  thickened  in  their  walls  by  depositions 
of  cellulose  and  other  matters,  according  to  their  age 


VEGETATIVE  ORGANS  OF  PLANTS.        255 

and  position,  and  are  sometimes  dotted  and  perforated, 
as  will  be  explained  hereafter — Fig.  53,  p.  301. 

Bast-Tissue  is  made  up  of  long  and  slender  cells, 
similar  to  those  of  wood-tissue,  but  commonly  more  del- 
icate and  flexible.  The  name  is  derived  from  the  occur- 
rence of  this  tissue  in  the  bast,  or  inner  bark.  Linena 
hemp,  and  most  textile  materials  of  vegetable  origin, 
cotton  excepted,  consist  of  bast-fibers.  Bast-cells  occupy 
a  place  in  rind,  corresponding  to  that  held  by  wood- 
cells  in  the  interior  of  the  stem — Fig.  49,  p.  293. 

Vascular  Tissue  is  the  term  applied  to  those  un- 
branched  Tubes  and  Ducts  which  are  found  in  all  the 
higher  orders  of  plants,  interpenetrating  the  cellular 
tissue.  There  are  several  varieties  of  ducts,  viz.,  dotted 
ducts,  ringed  or  annular  ducts,  and  spiral  ducts,  of 
which  illustrations  will  be  given  when  the  minute  struc- 
ture of  the  stem  comes  under  notice — Fig.  49,  p.  293. 

The  formation  of  vascular  tissue  takes  place  by  a  sim- 
ple alteration  in  cellular  tissue.  A  longitudinal  series  of 
adhering  cells  represents  a  tube,  save  that  the  bore  is 
obstructed  with  numerous  transverse  partitions.  By  the 
removal  or  perforation  of  these  partitions  a  tube  is  devel- 
oped. This  removal  or  perforation  actually  takes  place 
in  the  living  plant  by  a  process  of  absorption. 


CHAPTER  IIL 
THE  VEGETATIVE  ORGANS  OF  PLANTS. 

§   I- 

THE    BOOT. 

The  roots  of  plants,  with  few  exceptions,  from  the 
first  moment  of  their  development,  grow  downward.  In 
general,  they  require  a  moist  medium.  They  will  form 
in  water  or  in  moist  cotton,  and  in  many  cases  originate 
from  branches,  or  even  leaves,  when  these  parts  of  the 
plant  are  buried  in  the  earth  or  immersed  in  water.  It 
cannot  be  assumed  that  they  seek  to  avoid  the  light, 
because  they  may  attain  a  full  development  without 
being  kept  in  darkness.  The  action  of  light  upon  them, 
however,  appears  to  be  unfavorable  to  their  functions. 

The  Growth  of  Roots  occurs  mostly  by  lengthen- 
ing, and  very  little  or  very  slowly  by  increase  of  thick- 
ness. The  lengthening  is  chiefly  manifested  toward  the 
outer  extremities  of  the  roots,  as  was  neatly  demonstrated 
by  Wigand,  who  divided  the  young  root  of  a  sprouted 
pea  into  four  equal  parts  by  ink-marks.  After  three 
days,  the  first  two  divisions  next  the  seed  had  scarcely 
lengthened  at  all,  while  the  third  was  double,  and  the 
fourth  eight  times  its  previous  length.  Ohlerts  made 
precisely  similar  observations  on  the  roots  of  various 
kinds  of  plants.  The  growth  is  confined  to  a  space  of 
about  one-sixth  of  an  inch  from  the  tip.  (Linnea,  1837, 
pp.  609-631.)  This  peculiarity  adapts  the  roots  to 
extend  through  the  soil  in  all  directions,  and  to  occupy 
256 


VEGETATIVE  ORGANS  OF  PLANTS. 


257 


its  smallest  pores,  or  rifts.  It  is  likewise  the  reason  that 
a  root,  which  has  been  cut  off  in  transplanting  or  other- 
wise, never  afterwards  extends  in  length. 

Although  the  older  parts  of  the  roots  of  trees  and  of 
the  so-called  root-crops  acquire  a  considerable  diameter, 
the  roots  by  which  a  plant  feeds  are  usually  thread-like 
and  often  exceedingly  slender. 

Spongioles. — The  tips  of  the  rootlets  have  been 
termed  spongioles,  or  spongelets,  from  the  idea  that 
their  texture  adapts  them  especially  to  collect  food  for 
the  plant,  and  that  the  absorption  of  matters  from  the 
soil  goes  on  exclusively  through  them.  In  this  sense, 
spongioles  do  not  exist.  The  real  living  apex  of  the 
root  is  not,  in  fact,  the  outmost  extremity,  but  is  situ- 
ated a  little  within  that  point. 

Root-Cap. — The  extreme  end  of  the  root  usually  con- 
sists of  cells  that  have  become  loosened  and  in  part 
detached  from  the  proper  cell-tis- 
sue of  the  root,  which,  therefore, 
shortly  perish,  and  serve  merely 
as  an  elastic  cushion  or  cap  to 
protect  the  true  termination  or 
living  point  of  the  root  in  its  act 
of  penetrating  the  soil.  Fig.  36 
represents  a  magnified  section  of 
part  of  a  barley  root,  showing  the 
loose  cells  which  slough  off  from 
the  tip.  These  cells  are  filled 
with  air  instead  of  sap. 

A  striking  illustration  of  the 
root-cap  is  furnished  by  the  air- 
roots  of  the  so-called  Screw  Pine 
(Pandanus  odoratissimus),  exhibited  in  natural  dimen- 
sions, in  Fig.  37.  These  air-roots  issue  from  the  stem 
above  the  ground,  and,  growing  downwards,  enter  the 
soil,  and  become  roots  in  the  ordinary  sense, 

17  L 


Fig.  36. 


258 


HOW  CROPS  GROW. 


When  fresh,  the  diameter  of  the  root  is  quite  uni- 
form, but  the  parts  above  the  root-cap  shrink  on  dry- 
ing, while  the  root-cap  itself  retains 
nearly  its  original  dimensions,  and 
thus  reveals  its  different  structure. 

Distinction  between  Root  and 
Stem.— Not  all  the  subterranean 
parts  of  the  plant  are  roots  in  a 
proper  sense,  although  commonly 
spoken  of  as  such.  The  tubers  of 
the  pobato  and  artichoke,  and  the 
fleshy  horizontal  parts  of  the  sweet- 
flag  and  pepper-root,  are  merely 
underground  stems,  of  which  many 
varieties  exist. 

These  and  all  other  stems  are 
easily  distinguished  from  true  roots 
by  the  imbricated  buds,  of  which 
indications  may  usually  be  found  on 
their  surfaces,  e.  g.,  the  eyes  of  the 
potato-tuber.  TKe  side  or  second- 
ary roots  are  indeed  marked  in  their 
earliest  stages  by  a  protuberance  on 
the  primary  root,  but  these  have  noth- 
ing in  common  with  the  structure  of 
true  buds.  The  onion-bulb  is  itself 
a  fleshy  bud,  as  will  be  noticed  subse-  Fig.  37. 

quently.  The  true  roots  of  the  onion  are  the  fibers 
which,  issue  from  the  base  of  the  bulb.  The  roots  of 
many  plants  exhibit  no  buds  upon  their  surface,  and  are 
incapable  of  developing  them  under  any  conditions. 
Roots  of  other  plants,  such  as  the  plum,  apple,  and  pop- 
lar, may  produce  buds  when  cut  off  from  the  parent 
plant  during  the  growing  season.  The  roots  of  the 
former  perish  if  deprived  of  connection  with  the  stern 
and  leaves.  The  latter  may  strike  out  new  stems  and 


VEGETATIVE  ORGANS  OF  PLANTS.  259 

leaves  for  themselves.  Plants  like  the  plum  are,  there- 
fore, capable  of  propagation  by  root-cuttings,  i.  e.,  by 
placing  pieces  of  their  roots  in  warm  and  moist  earth. 

Tap-roots. — All  plants  whose  seeds  divide  into  two 
seed-leaves  or  Cotyledons,  and  whose  stems  increase 
externally  by  addition  of  new  rings  of  growth — the 
Dicotyledonous  plants,  or  Exogens — have,  at  first,  a  single 
descending  axis,  the  tap-root,  which  penetrates  vertically 
into  the  ground.  From  this  central  tap-root  lateral 
loots  branch  out  more  or  less  regularly,  and  these  lateral 
*oots  subdivide  again  and  again.  In  many  cases,  espec- 
ially at  first,  the  lateral  roots  issue  from  the  tap-root 
with  great  order  and  regularity,  as  much  as  is  seen  ii* 
the  branches  of  the  stem  of  a  fir-tree  or  of  a  young  grape- 
vine. In  older  plants,  this  order  is  lost,  because  the 
soil  opposes  mechanical  hindrances  to  regular  develop- 
ment. In  many  cases  the  tap-root  grows  to  a  great 
length,  and  forms  the  most  striking  feature  of  the  radi- 
cation  of  the  plant.  In  others  it  enters  the  ground  bufc 
a  little  way,  or  is  surpassed  in  extent  by  its  side  branches. 
The  tap-root  is  conspicuous  in  the  Canpda  thistle,  dock 
(Itumex),  and  in  seedling  fruit  trees.  The  upper  por- 
tion of  the  tap-root  of  the  beet,  turnip,  carrot,  and  rad- 
ish expands  under  cultivation,  and  becomes  a  fleshy, 
nutritive  mass,  in  which  lies  the  value  of  these  plants 
for  agriculture.  The  lateral  roots  of  other  plants,  as  of 
the  dahlia  and  sweet  potato,  swell  out  at  their  extremi- 
ties to  tubers. 

Crown  Roots. — Monocotyledonous  plants,  or  Endo* 
gens,  i.  e.,  plants  whose  embryos  have  only  one  seed- 
leaf,  or  Cotyledon,  and  whose  stems  do  not  increase  by 
external  additions,  such  as  the  cereals,  grasses,  lilies, 
palms,  etc.,  have  no  single  descending  axis  or  tap-root, 
but  produce  crown  roots,  i.  e.,  a  number  of  roots  issue 
at  once  from  the  base  of  the  stem.  This  is  strikingly 
Been  in  the  onion  and  hyacinth,  as  well  as  in  maize. 


260  HOW  CEOPS  GROW. 

Rootlets. — This  term  we  apply  to  the  slender  roots, 
but  a  few  inches  long,  which  are  formed  last  in  the 
order  of  growth,  and  correspond  to  the  larger  roots  as 
twigs  correspond  to  the  branches  of  the  stem. 

THE  OFFICES  OF  THE  ROOT  are  threefold : 

1.  To  fix  the  plant  in  the  earth  and  maintain  it  in  an 
erect  position. 

2.  To  absorb  nutriment  from  the  soil  for  the  growth 
of  the  entire  plant,  and, 

3.  In  case  of  many  plants,  especially  of  those  whose 
terms  of  life  extend  through  several  or  many  years,  to 
serve  as  a  store-house  for  the  future  use  of  the  plant. 

1.  The  Firmness  with  which  a  Plant  is  fixed  in 
the  Ground  depends  upon  the  nature  of  its  roots.     It 
is  easy  to  lift  an  onion  from  the  soil ;  a  carrot  requires 
much  more  force,  while  a  dock  may  resist  the  full 
strength  of  a  powerful  man.     A  small  beech  or  seedling 
apple  tree,  which  has  a  tap-root,  withstands  the  force  of 
a  wind  that  would  prostrate  a  maize-plant  or  a  poplar, 
which  has  only  side  roots.     In  the  nursery  it  is  the  cus- 
tom to  cut  off  the  tap-root  of  apple,  peach,  and  other 
trees,  when  very  young,  in  order  that  they  may  be  readily 
and  safely  transplanted  as  occasion  shall  require.     The 
depth  and  character  of  the  soil,  however,  to  a  certain 
degree  influence  the  extent  of  the  roots  and  the  tenacity 
of  their  hold.     The  roots  of  maize,  which  in  a  rich 
and  tenacious  earth  extend  but  two  or  three  feet,  have 
been  traced  to  a  length  of  ten  or  even  fifteen  feet  in 
a  light,  sandy  soil.     The  roots  of  clover,  and  especially 
those  of  alfalfa,  extend  very  deeply  into  the  soil,  and  the 
latter  acquire  in  some  cases  a  length  of  30  feet.     The 
roots  of  the  ash  have  been  known  as  much  as  95  feet 
long.     (Jour.  Roy.  Ag.  Soc.,  VI,  p.  342.) 

2.  Root-absorption. — The    Office   of    Absorbing 
Plant  Food  from  the  Soil  is  one  of  the  utmost  impor- 
tance, and  one  for  which  the  root  is  most  wisely  adapted 
by  the  following  particulars,  yia. : 


VEGETATIVE  ORGANS  OF  PLANTS. 

a.  The  Delicacy  of  its  Structure,  especially  that  of  the 
newer  portions,  the  cells  of  which  are  very  soft  and  ab- 
sorbent, as  may  be  readily  shown  by  immersing  a  young 
seedling  bean  in  solution  of  indigo,  when  the  roots 
shortly  acquire  a  blue  color  from  imbibing  the  liquid, 
while  the  stem  is  for  a  considerable  time  unaltered. 

It  is  a  common  but  erroneous  idea  that  absorption 
from  the  soil  can  only  take  place  through  the  ends  of  the 
roots — through  the  so-called  spongioles.  On  the  con- 
trary, the  extreme  tips  of  the  rootlets  cannot  take  up  liq- 
uids at  all.  (Ohlerts,  loc.  cit.,  see  p.  270.)  All  other 
parts  of  the  roots,  which  are  still  young  and  delicate  in 
surface-texture,  are  constantly  active  in  the  work  of  im- 
bibing nutriment  from  the  soil. 

In  most  perennial  plants,  indeed,  the  larger  branches 
of  the  roots  become  after  a  time  coated  with  a  corky  or 
otherwise  nearly  impervious  cuticle,  and  the  function  of 
absorption  is  then  transferred  to  the  rootlets.  This  is 
demonstrated  by  placing  the  old,  brown-colored  roots  of 
a  plant  in  water,  but  keeping  the  delicate  and  uiiindu- 
rated  extremities  above  the  liquid.  Thus  situated,  the 
plant  withers  nearly  as  soon  as  if  its  root- surf  ace  were  all 
exposed  to  the  air. 

b.  Its  Rapid  Extension  in  Length,  and  the  vast  Sur~ 
face  which  it  puts  in  contact  with  the  soil,  further  adapts 
the  root  to  the  work  of  collecting  food.     The  length  of 
roots  in  a  direct  line  from  the  point  of  their  origin  is 
not,  indeed,  a  criterion  by  which  to  judge  of  the  effi- 
ciency wherewith  the  plant  to  which  the*  belong  is  nour- 
ished ;  for  two  plants  may  be  equally  flourishing — be 
equally  fed  by  their  roots — when  these  organs,  in  one 
case,  reach  but  one  foot,  and  in  the  other  extend  two  feet 
from  the  stem  to  which  they  are  attached.     In  one  case, 
the  roots  would  be  fewer  and  longer;  in  the  other, 
ehortei1  and  more  numerous.     Their  aggregate  length, 
or,   more  correctly,   the  aggregate   absorbing  surface, 
would  be  nearly  the  same  in  both. 


262  HOW  CROPS  GROW. 

The  Medium  in  which  Roots  Grow  has  a  great  influ- 
ence on  their  extension.  When  they  are  situated  in  con- 
centrated solutions,  or  in  a  very  fertile  soil,  they  are 
short,  and  numerously  branched.  Where  their  food  is 
sparse,  they  are  attenuated,  and  bear  a  comparatively 
small  number  of  rootlets.  Illustrations  of  the  former 
condition  are  often  seen ;  moist  bones  and  masses  of 
manure  are  not  infrequently  found,  completely  covered 
and  penetrated  by  a  fleece  of  stout  roots.  On  the  other 
hand,  the  roots  which  grow  in  poor,  dry  soils  are  very 
long  and  slender. 

Nobbe  has  described  some  experiments  which  com- 
pletely establish  the  point  under  notice.  (Vs.  St.,  IV, 
p.  212. )  He  allowed  maize  to  grow  in  a  poor  clay  soil, 
contained  in  glass  cylinders,  each  vessel  having  in  it  a 
quantity  of  a  fertilizing  mixture  disposed  in  some  pecu- 
liar manner  for  the  purpose  of  observing  its  influence  on 
the  roots.  When  the  plants  had  been  nearly  four  months 
in  growth,  the  vessels  were  placed  in  water  until  the  earth 
was  softened,  so  that  by  gentle  agitation  it  could  be  com- 
pletely removed  from  the  roots.  The  latter,  on  being 
suspended  in  a  glass  vessel  of  water,  assumed  nearly  the 
position  they  had  occupied  in  the  soil,  and  it  was  ob- 
served that,  where  the  fertilizer  had  been  thoroughly 
mixed  with  the  soil,  the  roots  uniformly  occupied  its 
entire  mass.  Where  the  fertilizer  had  been  placed  in  a 
horizontal  layer  at  the  depth  of  about  one  inch,  the  roots 
at  that  depth  formed  a  mat  of  the  finest  fibers.  Where 
the  fertilizer  was  situated  in  a  horizontal  layer  at  half  the 
depth  of  the  vessel,  just  there  the  root  system  was  sphe- 
roidally  expanded.  In  the  cylinders  where  the  fertilizer 
formed  a  vertical  layer  on  the  interior  walls,  the  external 
roots  were  developed  in  numberless  ramifications,  while 
the  interior  roots  were  comparatively  unbranched.  In 
pots,  where  the  fertilizer  was  disposed  as  a  central  vertical 
core,  the  inner  roots  were  far  more  greatly  developed 


VEGETATIVE  ORGANS  OF  PLANTS.  263 

than  the  outer  ones.  Finally,  in  a  vessel  where  the  fer- 
tilizer was  placed  in  a  horizontal  layer  at  the  bottom, 
the  roots  extended  through  the  soil,  as  attenuated  and 
slightly  branched  fibers,  until  they  came  in  contact  with 
the  lower  stratum,  where  they  greatly  increased  and  ram- 
ified. In  all  cases,  the  principal  development  of  the 
roots  occurred  in  the  immediate  vicinity  of  the  material 
which  could  furnish  them  with  nutriment. 

It  has  often  been  observed  that  a  plant  whose  aerial 
branches  are  symmetrically  disposed  about  its  stem,  has 
the  larger  share  of  its  roots  on  one  side,  and  again  we  find 
roots  which  are  thick  with  rootlets  on  one  side  and 
nearly  devoid  of  them  on  the  other. 

Apparent  Search  for  Food. — It  would  almost  appear, 
on  superficial  consideration,  that  roots  are  endowed  with 
a  kind  of  intelligent  instinct,  for  they  seem  to  go  in 
search  of  nutriment. 

The  roots  of  a  plant  make  their  first  issue  independ- 
ently of  the  nutritive  matters  that  may  exist  in  their 
neighborhood.  They  are  organized  and  put  forth  from 
the  plant  itself,  no  matter  how  fertile  or  sterile  the  me- 
dium that  surrounds  them.  When  they  attain  a  certain 
development,  they  are  ready  to  exercise  their  office  of 
collecting  food.  If  food  be  at  hand,  they  absorb  it,  and, 
together  with  the  entire  plant,  are  nourished  by  it — they 
grow  in  consequence.  The  more  abundant  the  food,  the 
better  they  are  nourished,  and  the  more  they  multiply. 
The  plant  sends  out  rootlets  in  all  directions ;  those 
which  come  in  contact  with  food,  live,  enlarge,  and  ram- 
ify ;  those  which  find  no  nourishment,  remain  undevel- 
oped or  perish. 

The  Quantity  of  Roots  actually  belonging  to  any  Plant 
is  usually  far  greater  than  can  be  estimated  by  roughly 
lifting  them  from  the  soil.  To  extricate  the  roots  of 
wheat  or  clover,  for  example,  from  the  earth,  completely, 
is  a  matter  of  extreme  difficulty.  Schubart  was  the  first 


264  HOW  CROPS  GROW. 

to  make  satisfactory  observations  on  the  roots  of  several 
important  crops,  growing  in  the  field.  He  separated 
them  from  the  soil  by  the  following  expedient :  An  exca- 
vation was  made  in  the  field  to  the  depth  of  6  feet,  and 
a  stream  of  water  was  directed  against  the  vertical  wall 
of  soil  until  it  was  washed  away,  so  that  the  roots  of  the 
plants  growing  in  it  were  laid  bare.  The  roots  thus  ex- 
posed in  a  field  of  rye,  in  one  of  beans,  and  in  a  bed  of 
garden  peas,  presented  the  appearance  of  a  mat  or  felt  of 
white  fibers,  to  a  depth  of  about  4  feet  from  the  surface 
of  the  ground.  The  roots  of  winter  wheat  he  observed 
as  deep  as  7  feet,  in  a  light  subsoil,  forty-seven  days  after 
sowing.  The  depth  of  the  roots  of  winter  wheat,  winter 
rye,  and  winter  colza,  as  well  as  of  clover,  was  3  to  4  feet. 
The  roots  of  clover,  one  year  old,  were  3£  feet  long,  those 
of  two-year-old  clover  but  four  inches  longer.  The  quan- 
tity of  roots  in  per  cent  of  the  entire  plant  in  the  dry 
state  was  found  to  be  as  follows.  (Chem.  Ackersmann, 
I,  p.  193.) 

Winter  wheat— examined  last  of  April 40% 

«  »  »  "  "  May 22" 

«  rye  "  "  "April 34" 

Peas  examined  four  weeks  after  sowing 44  " 

««  "  at  the  time  of  blossom 24" 

Hellriegel  has  likewise  studied  the  radication  of  barley 
and  oats  (Hoff,  Jakresbericht,  1864,  p.  106.)  He  raised 
plants  in  large  glass  pots,  and  separated  their  roots  from 
the  soil  by  careful  washing  with  water.  He  observed 
that  directly  from  the  base  of  the  stem  20  to  30  roots 
branch -off  sideways  and  downward.  These  roots,  at 
their  point  of  issue,  have  a  diameter  of  ^  of  an  inch, 
but  a  little  lower  the  diameter  diminishes  to  about  TJ^  of 
an  inch.  Retaining  this  diameter,  they  pass  downward, 
dividing  and  branching  to  a  certain  depth.  From  these 
main  roots  branch  out  innumerable  side  roots,  which 
branch  again,  and  so  on,  filling  every  crevice  and  pore  of 
the  soil. 


VEGETATIVE  OKGANS  OF  PLANTS. 


265 


To  ascertain  the  total  length  of  root,  Hellriegel  weighed 
and  ascertained  the  length  of  selected  average  portions. 
"Weighing  then  the  entire  root-system,  he  calculated  the 
entire  length.  He  estimated  the  length  of  the  roots  of  a 
vigorous  barley  plant  at  128  feet,  that  of  an  oat  plant  at 
150  feet.*  He  found  that  a  small  bulk  of  good  fine  £oi' 
sufficed  for  this  development ;  ^5  cubic  foot  (4  -{-  4  -j-  2; 
in.)  answered  for  a  barley  plant,  ^  cubic  foot  for  an 
oat  plant,  in  these  experiments. 

Hellriegel  observed  also  that  the  quality  of  the  soil  in- 
fluenced the  development.  In  rich,  porous,  garden-soil, 
a  barley  plant  produced  128  feet  of 
roots,  but  in  a  coarse-grained,  com- 
pacter  soil,  a  similar  plant  had  but  80 
feet  of  roots. 

Root  Hairs. — The  real  absorbent 
surface  of  roots  is,  in  most  cases,  not 
to  be  appreciated  without  microscopic 
aid.  The  roots  of  the  onion  and  of 
many  other  bulbs,  i.  e. ,  the  fibers  Avhich 
issue  from  the  base  of  the  bulbs,  are  per- 
fectly smooth  and  unbranched  through- 
out their  entire  length.  Other  agricul- 
tural plants  have  roots  which  are  not 
only  visibly  branched,  but  whose  finest 
fibers  are  more  or  less  thickly  covered 
with  minute  hairs,  scarcely  perceptible 
to  the  unassisted  eye.  These  root-hairs 
consist  always  of  tubular  elongations  of 
the  external  root-cells,  and  through 
them  the  actual  root-surface  exposed 
to  the  soil  becomes  something  almost 
Fig.  38.  incalculable.  The  accompanying  fig- 

ures illustrate  the  appearance  of  root-hairs. 
Fig.  38  represents  a  young  mustard  seedling.     A  is 

•Rhenish,  34  =  46  Bnglish  feet. 


266  HOW  CROPS  GROW. 

the  plant,  as  carefully  lifted  from  the  sand  in  which  it 
grew,  and  B  the  same  plant,  freed  from  adhering  soil 
by  agitating  in  water.  The  entire  root,  save  the  tip, 
is  thickly  beset  with  hairs.  In  Fig.  39  a  minute  portion 
of  a  barley-root  is  shown  highly  magnified.  The  hairs 
are  seen  to  be  slender  tubes  that  proceed  from,  and  form 
part  of,  the  outer  cells  of  the  root. 

The  older  roots  lose  their  hairs,  and  suffer  a  thicken- 
ing of  the  outermost  layer  of  cells.  These  dense-walled 
and  nearly  impervious  cells  cohere  together  and  consti- 
tute a  rind,  which  is  not  found  in  the  young  and  active 
roots. 

As  to  the  development  of  the 
root-hairs,  they  are  more  abund- 
ant in  poor  than  in  good  soils, 
and  appear  to  be  most  numer- 
ously produced  from  roots  which 
have  otherwise  a  dense  and  un- 
absorbent  surface.  The  roots  of 
those  plants  which  are  destitute 
of  hairs  are  commonly  of  consid- 
erable thickness  and  remain 
white  and  of  delicate  texture, 
preserving  their  absorbent  power  Flg-  3a 

throughout  the  whole  time  that  the  plant  feeds  from  the 
soil,  as  is  the  case  with  the  onion. 

The  Silver  Fir  (Abies  Picea)  has  no  root-hairs,  but  its 
rootlets  are  covered  with  a  very  delicate  cuticle  highly 
favorable  to  absorption.  The  want  of  root-hairs  is  fur- 
ther compensated  by  the  great  number  of  rootlets  which 
are  formed,  and  which,  perishing  mostly  before  they  be- 
come superficially  indurated,  are  continually  replaced  by 
new  ones  during  the  growing  season.  (Schacht,  Der 
Baiim,  p.  165.) 

Contact  of  Roots  with  the  Soil — The  root-hairs,  as 
they  extend  into  the  soil,  are  naturally  brought  into  close 


VEGETATIVE  ORGANS  OF  PLANTS.  267 

if' 


268 


HOW  CROPS  GROW. 


contact  with  its  particles.  This  contact  is  much  more 
intimate  than  has  been  usually  supposed.  If  we  care- 
fully lift  a  young  wheat-plant  from  dry  earth,  we  notice 
that  each  rootlet  is  coated  with  an  envelope  of  soil.  This 
adheres  with  considerable  tenacity,  so  that  gentle  shak- 
ing fails  to  displace  it,  and  if  it  be  mostly  removed  by 


Fig.  4m. 

vigorous  agitation  or  washing,  the  root-hairs  are  either 
found  to  be  broken,  or  in  many  places  inseparably  at- 
tached to  the  particles  of  earth. 
Fig.  40  exhibits  the  appearao.ee  of  a  young  wheat- 


VEGETATIVE  OBGANS  OF  PLANTS. 


269 


plant  as  lifted  from  the  soil  and  pretty  strongly  shaken. 
S,  the  seed ;  b,  the  blade ;  e,  roots  covered  with  hairs 
and  enveloped  in  soil.  Only  the  growing  tips  of  the 
roots,  w,  which  have  not  put  forth  hairs,  come  out  clean 
of  soil.  Fig.  41  represents  the  roots  of  a  wheat-plant 
one  month  older  than  those  of  the  previous  figure.  In 
this  instance  not  only  the  root-tips  are  naked  as  before, 
but  the  older  parts  of  the  primary  roots,  e,  and  of  the 
secondary  roots,  n,  no  longer  retain  the  particles  of  soil ; 
the  hairs  upon  them  being,  in  fact,  dead  and  decom- 
posed. The  newer  parts  of  the  root  alone  are  clothed 
with  active  hairs,  and  to  these  the  soil  is  firmly  attached 
as  before.  The  next  illustration,  Fig.  42,  exhibits  the 
appearance  of  root-hairs  with  ad- 
hering particles  of  earth,  when  mag- 
nified 800  diameters  :  A,  root-hairs 
of  wheat-seedling,  like  Fig.  40;  B, 
of  oat-plant,  both  from  loamy  soil. 
Here  is  plainly  seen  the  intimate 
attachment  of  the  soil  and  root- 
hairs.  The  latter,  in  forcing  their 
way  against  considerable  pressure, 
often  expand  around,  and  partially 
envelop,  the  particles  of  earth. 
(Sachs's  Exp.  Phys.  d.  Pflanzen.) 
Imbibition  of  water  by  the  root. — 
The  force  with  which  active  roots 
imbibe  the  water  of  the  soil  is 
sufficient  to  force  the  liquid  upward 
into  the  stem  and  to  exert  a  continu- 
al pressure  on  all  parts  of  the  plant. 
When  the  stem  of  a  plant  in  vigor- 
ous growth  is  cut  off  near  the  root, 
and  a  pressure-gauge  is  attached  to 
it,  as  in  Fig.  43,  we  have  the  means  of  observing  and 
measuring  the  force  with  which  the  roots  absorb  water. 


Fig.  43. 


270  HOW  CROPS  GROW. 

The  pressure-gauge  contains  a  quantity  of  mercury  in 
the  middle  reservoir,  J,  and  the  tube,  c.  It  is  attached 
to  the  stem  of  the  plant,  p,  by  a  stout  india-rubber 
pipe,  <?.*  For  accurate  measurements,  the  space  a  and 
b  should  be  filled  with  water.  Thus  arranged,  it  is  found 
that  water  will  enter  a  through  the  stem,  and  the  mer- 
cury will  rise  in  the  tube,  e,  until  its  pressure  becomes 
sufficient  to  balance  the  absorptive  power  of  the  roots. 
Stephen  Hales,  who  first  experimented  in  this  manner 
(1721)  found  in  one  instance  that  the  pressure  exerted 
on  a  gauge,  attached  in  spring  time  to  the  stump  of  a 
grape-vine,  supported  a  column  of  mercury  32£  inches 
high,  which  is  equal  to  a  column  of  water  of  36^  feet. 
Hofmeister  obtained  on  other  plants,  rooted  in  pots,  the 
following  results : 

Bean  (Phaseolus  multiflorus)   6  inches  of  mercury. 

Nettle 14       "  " 

Vine 29       "  " 

The  seat  of  absorption  Dutrochet  demonstrated  to  be 
the  surface  of  the  young  and  active  roots.  At  least,  he 
found  that  absorption  was  exerted  with  as  much  force 
when  the  gauge  was  applied  to  near  the  lower  extremity 
of  a  root  as  when  attached  in  the  vicinity  of  the  stem. 
In  fact,  when  other  conditions  are  alike,  the  column  of 
liquid  sustained  by  the  roots  of  a  plant  is  greater  the  less 
the  length  of  stem  that  remains  attached  to  them.  The 
stem  thus  resists  the  rise  of  liquid  in  the  plant. 

While  the  seat  of  absorptive  power  in  the  root  lies 
near  the  extremities,  it  appears  from  the  experiments  of 
Ohlerts  that  the  extremities  themselves  are  incapable  of 
imbibing  water.  In  trials  with  young  pea,  flax,  lupine 
and  horseradish  plants  with  unbranched  roots,  he  found 
that  they  withered  speedily  when  the  tips  of  the  roots 
were  immersed  for  about  one-fourth  of  an  inch  in  water, 

*For  experimenting  on  small  plants,  a  simple  tube  of  glass  may  be 
adjusted  to  the  stump  vertically  by  help  of  a  rubber  connector. 


VEGETATIVE  OftGAHS  OF  PLANTS.  271 

the  remaining  parts  being  in  moist  air.  Ohlerts  like» 
wise  proved  that  these  plants  flourish  when  only  the 
middle  part  of  their  roots  is  immersed  in  water.  Keep- 
ing the  root-tips,  the  so-called  spongioles,  in  the  air,  or 
cutting  them  away  altogether,  was  without  apparent 
effect  on  the  freshness  and  vi£or  of  the  plants.  The 
absorbing  surface  would  thus  appear  to  be  confined  to 
those  portions  of  the  root  upon  which  the  development 
of  root-hairs  is  noticed. 

The  absorbent  force  is  manifested  by  the  active  root- 
lets, and  most  vigorously  when  these  are  in  the  state  of 
most  rapid  development.  For  this  reason  we  find,  in 
case  of  the  vine,  for  example,  that  during  the  autumn, 
when  the  plant  is  entering  upon  a  period  of  repose  from 
growth,  the  absorbent  power  is  trifling.  Sometimes 
water  is  absorbed  at  the  roots  so  forcibly  as  not  only  to 
distend  the  plant  to  the  utmost,  but  to  cause  the  sap  of 
the  plant  to  exude  in  drops  upon  the  foliage.  This  may 
be  noticed  upon  newly-sprouted  maize,  or  other  cereal 
plants,  where  the  water  escapes  from  the  leaves  at  their 
extreme  tips,  especially  when  the  germination  has  pro- 
ceeded under  the  most  favorable  conditions  for  rapid 
development. 

The  bleeding  of  the  vine,  when  severed  in  the  spring- 
time, the  abundant  flow  of  sap  from  the  sugar-maple 
and  the  water-elm,  are  striking  illustrations  of  this 
imbibition  of  water  from  the  soil  by  the  roots.  These 
examples  are,  indeed,  exceptional  in  degree,  but  not  in 
kind.  Hofmeister  has  shown  that  the  bleeding  of  a  sev- 
ered stump  is  a  general  fact,  and  occurs  with  all  plants 
when  the  roots  are  active,  when  the  soil  can  supply  them 
abundantly  with  water,  and  when  the  tissues  above  the 
absorbent  parts  are  full  of  this  liquid.  When  it  is  other- 
wise, water  may  be  absorbed  from  the  gauge  into  the 
stem  and  large  roots,  until  the  conditions  of  activity  are 
renewed. 


272  HOW  CEOPS  GROW. 

Of  the  external  circumstances  that  affect  this  absorp- 
tive power,  heat  and  light  would  appear  to  be  influential. 
By  observing  a  gauge  attached  to  the  stump  of  a  plant; 
during  a  clear  summer  day,  it  will  be  usually  noticed 
that  the  mercury  begins  to  rise  in  the  morning  as  the 
sun  warms  the  soil,  and  continues  to  ascend  for  a  num- 
ber of  hours,  but  falls  again  as  the  sun  declines.  Sachs 
found  in  some  of  his  experiments  that,  in  case  of  potted 
tobacco  and  squash  plants,  absorption  was  nearly  or 
entirely  suppressed  by  cooling  the  roots  to  41°  F.,  but 
was  at  once  renewed  by  plunging  the  pots  into  warm 
water. 

The  external  supplies  of  water, — in  case  a  plant  is 
stationed  in  the  soil,  the  degree  of  moisture  contained  in 
this  medium, — obviously  must  influence  any  manifesta- 
tion of  the  imbibing  force.  But  full  investigation  shows 
that  this  regular  daily  fluctuation  is  a  habit  of  the  plant 
which  is  independent  of  small  changes  of  temperature 
and  even  of  considerable  variation  in  the  amount  of  mois- 
ture of  the  soil. 

The  rate  of  absorption  is  subject  to  changes  depend- 
ent on  causes  not  well  understood.  Sachs  observed 
that  the  amount  of  liquid  which  issued  from  potato 
stalks  cut  off  just  above  the  ground  underwent  great 
and  continual  variation  from  hour  to  hour  (during  rainy 
weather)  when  the  soil  was  saturated  with  water  and 
when  the  thermometer  indicated  a  constant  temperature. 
Hofmeister  states  that  the  formation  of  new  roots  and 
buds  on  the  stump  is  accompanied  by  a  sinking  of  the 
water  in  the  pressure-gauge. 

Absorption  of  Nutriment  from  the  Soil. — The  food  of 
the  plant,  so  far  as  it  is  derived  from  the  soil,  enters  it 
in  a  state  of  solution,  and  is  absorbed  with  the  water 
which  is  taken  up  by  the  rootlets.  The  absorption  of 
the  matters  dissolved  in  water  is  in  some  degree  inde- 
pendent of  the  absorption  of  the  water  itself,  the  plant 


VEGETATIVE  OBGANS  OF  PLANTS.       273 

having  apparently,  to  a  certain  extent,  a  selective  power. 
See  p.  401. 

3.  The  Root  as  a  Magazine. — In  Fleshy  Tap- 
Roots,  like  those  of  the  carrot,  beet,  and  turnip,  the 
absorption  of  nutriment  from  the  soil  takes  place  princi- 
pally, if  not  entirely,  by  means  of  the  slender  rootlets 
which  proceed  abundantly  from  all  their  surface,  and 
especially  from  their  lower  extremities,  while  the  older 
fleshy  part  serves  as  a  magazine  in  which  large  quantities 
of  carbhydrates,  etc.,  are  stored  up  during  the  first  year's 
growth  of  these  biennial  plants,  to  supply  the  wants  of 
the  flowers  and  seed  which  are  developed  the  second  year. 
When  one  of  these  roots,  put  into  the  ground  for  a  sec- 
ond year,  has  produced  seed,  it  is  found  to  be  quite 
exhausted  of  the  nutritive  matters  which  it  previously 
contained  in  so  large  quantity. 

Root  Tulers,  like  those  of  the  dahlia  and  sweet  potato, 
are  fleshy  enlargements  of  lateral  or  secondary  roots 
filled  with  reserve  material,  from  which  buds  and  new 
stems  may  develop.  Small  tubers  (Tubercles)  are  fre- 
quently formed  on  the  roots  of  the  garden  bean 
(Phaseolus). 

In  cultivation,  the  farmer  not  only  greatly  increases 
the  size  of  these  roots  and  the  stores  of  organic  nutritive 
materials  they  contain,  but,  by  removing  them  from  the 
ground  in  autumn,  he  employs  to  feed  himself  and  his 
cattle  the  substances  that  nature  primarily  designed  to 
nourish  the  growth  of  flowers  and  seeds  during  another 
summer. 

Soil-Roots  ;  Water-Roots  ;  Air-Roots. — We  may 
distinguish,  according  to  the  medium  in  which  they  are 
formed  and  grow,  three  kinds  of  roots,  viz.:  soil-roots, 
water-roots,  and  air-roots. 

Most  agricultural  plants,  and  indeed  by  far  the  greater 
number  of  all  plants  found  in  temperate  climates,  have 
roots  adapted  especially  to  the  soil,  and  which  perish  by 
IS 


274  HOW  CROPS  GKOW. 

short  exposure  to  dry  air,  or  rot,  if  long  immersed  in 
wate.r.  Many  aquatic  plants,  on  the  other  hand,  speed- 
ily die  when  their  roots  are  removed  from  water,  or  from 
earth  saturated  with  water,  and  exposed  to  the  atmos- 
phere or  stationed  in  earth  of  the  usual  dryness. 

Air-roots  are  not  common  except  among  tropical  plants 
or  under  tropical  conditions  of  heat  and  moisture.  In- 
dian corn,  when  thickly  planted  and  of  rank  growth, 
often  throws  out  roots  from  the  lower  joints  of  the  stem, 
which  extend  through  the  air  several  inches  before  they 
reach  the  soil.  The  same  may  be  observed  of  many  com- 
mon plants,  as  the  oat,  grape,  potato,  and  buckwheat, 
when  they  long  remain  in  hot,  moist  air.  The  Banyan- 
tree  of  India  sends  out  from  its  branches,  vertically, 
pendants  several  yards  long  which  penetrate  the  earth 
and  there  become  soil-roots. 

On  the  other  hand,  various  tropical  plants,  especially 
Orchids,  emit  roots  which  hang  free  in  the  air  and  never 
reach  the  earth.  In  the  humid  forest  ravines  of  Madeira 
and  Teneriffe,  the  Laurus  Canariensis,  a  large  tree, 
sends  out  from  its  stem,  during  the  autumn  rains,  a  pro- 
fusion of  fleshy  air-roots,  which  cover  the  trunk  with 
their  interlacing  branches  and  grow  to  an  inch  in  thick- 
ness. The  following  summer  they  dry  away  and  fall  to 
the  ground,  to  be  replaced  by  new  ones  in  the  ensuing 
autumn.  (Schacht,  Der  Baum,  p.  172.) 

A  plant,  known  to  botanists  as  the  Zamia  splralis,  not 
only  throws  out  air-roots,  c  c,  Fig.  44,  from  the  crown  of 
the  main  soil-root,  but  the  side  rootlets,  J,  after  extend- 
ing some  distance  horizontally  in  the  soil,  send,  from  the 
same  point,  roots  downward  and  upward,  the  latter  of 
which,  d,  pass  into  and  remain  permanently  in  the  air. 
a  is  the  stem  of  the  plant.  (Schacht,  Anatomie  der 
Gewachse,  Bd.  II,  p.  151.) 

The  formation  of  air-roots  may  be  very  easily  observed 
by  placing  water  to  the  depth  of  half  an  inch  in  a  tall 


VEGETATIVE  OBGAtfS  OF  PLANTS. 


vial,  inserting  a  sprig  of  the  common  greenhouse-plant 
Tradescantia  zebrina,  so  that  the  cut  end  of  the  stem 
shall  stand  in  the  water,  and  finally  corking  the  vial  air- 
tight. The  plant,  which  is  very  tenacious  of  life,  and 
usually  grows  well  in  spite  of  all  neglect,  is  not  checked 
in  its  vegetative  development  by  the  treatment  just  de- 
scribed, but  immediately  begins  to  adapt  itself  to  its 
new  circumstances.  In  a  few  days,  if  the  temperature 
be  70°  or  thereabout,  air -roots  will  be  seen  to  issue  from 
the  joints  of  the  stem.  These  are  fringed  with  a  profu- 
sion of  delicate  hairs,  and  rapidly  extend  to  a  length  of 
from  one  to  two  inches.  The  lower  ones,  if  they  chance 


Fig.  44. 

to  penetrate  the  water,  become  discolored  and  decay  ;  th& 
others,  however,  remain  for  a  long  time  fresh,  and  of  a 
white  color. 

Some  plants  have  roots  which  are  equally  able  to  exist 
and  perform  their  functions,  whether  in  the  soil  or  sub- 


276  HOW  CROPS  GROW. 

merged  in  water.  Many  forms  of  vegetation  found  in 
our  swamps  and  marshes  are  of  this  kind.  Of  agricul- 
tural plants,  rice  is  an  example  in  point.  Rice  will  grow 
in  a  soil  of  ordinary  character,  in  respect  of  moisture,  as 
the  upland  cotton-soils,  or  even  the  pine-barrens  of  the 
Carolinas.  It  flourishes  admirably  in  the  tide-swamps  of 
the  coast,  where  the  land  is  laid  under  water  for  weeks 
at  a  time  during  its  growth,  and  it  succeeds  equally  well 
in  fields  which  are  flowed  from  the  time  of  planting  to 
that  of  harvesting.  (Eussell,  North  America,  its  Agri- 
culture and  Climate,  p.  176.)  The  willow  and  alder, 
trees  which  grow  on  the  margins  of  streams,  send  a  part 
of  their  roots  into  soil  that  is  constantly  saturated  with 
water,  or  into  the  water  itself ;  while  others  occupy  the 
merely  moist  or  even  dry  earth. 

Plants  that  customarily  confine  their  growth  to  the 
soil  occasionally  throw  out  roots  as  if  in  search  of  water, 
and  sometimes  choke  up  drain-pipes  or  even  wells  by  the 
profusion  of  water-roots  which  they  emit.  At  Welbeck, 
England,  a  drain  was  completely  stopped  by  roots  of 
horse-radish  plants  at  a  depth  of  7  feet.  At  Thorn sby 
Park,  a  drain  16  feet  deep  was  stopped  entirely  by  the 
roots  of  gorse,  growing  at  a  distance  of  6  feet  from  the 
drain.  (Jour.  Roy.  Ag.  Soc.,  I,  p.  364.)  In  New 
Haven,  Connecticut,  certain  wells  are  so  obstructed  by  the 
aquatic  roo,ts  of  the  elm  trees  as  to  require  cleaning  out 
every  two  or  three  years.  This  aquatic  tendency  has 
been  repeatedly  observed  in  the  poplar,  cypress,  laurel, 
turnip,  mangel-wurzel,  and  various  grasses. 

Henrici  surmised  that  the  roots  which  most  cultivated 
plants  send  down  deep  into  the  soil,  even  when  the  latter 
is  by  no  means  porous  or  inviting,  are  designed  especially 
to  bring  up  water  from  the  subsoil  for  the  use  of  the 
plant.  He  devised  the  following  experiment,  which  ap- 
pears to  prove  the  truth  of  this  view.  On  the  13th  of 
May,  1862,  a  young  raspberry  plant,  having  but  two 


VEGETATIVE  ORGANS  OF  PLANTS.  275 

leaves,  was  transplanted  into  a  large  glass  funnel  filled 
with  garden  soil,  the  throat  of  the  funnel  being  closed 
with  a  paper  filter.  The  funnel  was  supported  in  the 
mouth  of  a  large  glass  jar,  and  its  neck  reached  nearly  to 
the  bottom  of  the  latter,  where  it  just  dipped  into  a 
quantity  of  water.  The  soil  in  the  funnel  was  at  first 
kept  moderately  moist  by  occasional  waterings.  The 
plant  remained  fresh  and  slowly  grew,  putting  forth  new 
leaves.  After  the  lapse  of  several  weeks,  four  strong 
roots  penetrated  the  filter  and  extended  down  the  empty 
funnel-neck,  through  which  they  emerged,  on  the  21st 
of  June,  and  thenceforward  spread  rapidly  in  the  water 
of  the  jar.  From  this  time  on,  the  soil  was  not  watered 
any  more,  but  care  was  taken  to  maintain  the  supply  in 
the  jar.  The  plant  continued  to  develop  slowly ;  its 
leaves,  however,  did  not  acquire  a  vivid  green  color,  but 
remained  pale  and  yellowish  ;  they  did  not  wither  until 
the  usual  time,  late  in  autumn.  The  roots  continued  to 
grow,  and  filled  the  water  more  and  more.  Near  the 
end  of  December  the  plant  had  seven  or  eight  leaves,  and 
a  height  of  eight  inches.  The  water- roots  were  vigorous, 
very  long,  and  beset  with  numerous  fibrils  and  buds.  In 
the  funnel  tube  the  roots  made  a  perfect  tissue  of  fibers. 
In  the  dry  earth  of  the  funnel  they  were  less  extensively 
developed,  yet  exhibited  some  juicy  buds.  The  stem 
and  the  young  axillary  leaf -buds  were  also  full  of  sap. 
The  water-roots  being  cut  away,  the  plant  was  put  into 
garden  soil  and  placed  in  a  conservatory,  where  it  grew 
vigorously,  and  in  May  bore  two  offshoots.  (Hennefierg's 
Jour,  fur  Landwirfhschaft,  1863,  p.  280.)  This  growth 
towards  water  must  be  accounted  for  on  the  principles 
asserted  in  the  paragraph,  Apparent  Search  for  Food 
(p.  263). 

The  seeds  of  many  ordinary  land  plants — of  plants, 
indeed,  that  customarily  grow  in  a  dry  soil,  such  as  the 
bean,  squash,  maize,  etc. — will  readily  germinate  in 


278  HOW  CROPS  GROW. 

moist  cotton  or  sawdust,  and  if,  when  fairly  sprouted, 
the  young  plants  have  their  roots  suspended  in  water, 
taking  care  that  the  seed  and  stem  are  kept  above  the 
liquid,  they  will  continue  to  grow,  and  with  due  supplies 
of  nutriment  will  run  through  all  the  customary  stages 
of  development,  produce  abundant  foliage,  blossoms,  and 
perfect  seeds,  without  a  moment's  contact  of  their  roots 
with  soil.  (See  Water  Culture,  p.  181.) 

In  plants  thus  growing  with  their  roots  in  a  liquid 
medium,  after  they  have  formed  several  large  leaves,  be 
carefully  transplanted  to  the  soil,  they  wilt  and  perish, 
unless  frequently  watered ;  whereas  similar  plants,  started 
in  the  soil,  may  be  transplanted  without  suffering  in  the 
slightest  degree,  though  the  soil  be  of  the  usual  dryness, 
and  receive  no  water. 

The  water-bred  seedlings,  if  abundantly  watered  as 
often  as  the  foliage  wilts,  recover  themselves  after  a  time, 
and  thenceforward  continue  to  grow  without  the  need  of 
watering. 

It  might  appear  that  the  first-formed  water-roots  are 
incapable  of  feeding  the  plant  from  a  dry  soil,  and  hence 
the  soil  must  be  at  first  profusely  watered  ;  after  a  time, 
however,  new  roots  are  thrown  out,  which  are  adapted  to 
the  altered  situation  of  the  plant,  and  then  the  growth 
proceeds  in  the  usual  manner. 

The  reverse  experiment  would  seem  to  confirm  this 
view.  If  a  seedling  that  has  grown  for  a  short  time  only 
in  the  soil,  so  that  its  roots  are  but  twice  or  thrice 
branched,  have  these  immersed  in  water,  the  roots 
already  formed  mostly  or  entirely  perish  in  a  short  time. 
They  indeed  absorb  water,  and  the  plant  is  sustained  by 
them,  but  immediately  new  roots  grow  from  the  crown 
with  great  rapidity,  and  take  the  place  of  the  original 
roots,  which  become  disorganized  and  useless.  It  is, 
however,  only  the  young  and  active  rootlets,  and  those 
covered  with  hairs,  which  thus  refuse  to  live  in  water, 


VEGETATIVE  OBGANS  OF  PLANTS.  279 

The  older  parts  of  the  roots,  which  are  destitute  of  fibrils 
and  which  have  nearly  ceased  to  be  active  in  the  work  of 
absorption,  are  not  affected  by  the  change  of  circum- 
stance. These  facts,  which  are  due  to  the  researches  of 
Dr.  Sachs  (Vs.  St.,  II,  p.  13),  would  naturally  lead  to 
the  conclusion  that  the  absorbent  surface  of  the  root  un- 
dergoes some  structural  change,  or  produces  new  roots 
with  modified  characters,  in  order  to  adapt  itself  to  the 
medium  in  which  it  is  placed.  It  would  appear  that 
when  this  adaptation  proceeds  rapidly  the  plant  is  not 
permanently  retarded  in  its  growth  by  a  gradual  change 
in  the  character  of  the  medium  which  surrounds  its 
roots,  as  may  happen  in  case  of  rice  and  marsh-plants, 
when  the  saturated  soil  in  which  they  may  be  situated  at 
one  time  is  slowly  dried.  Sudden  changes  of  medium 
about  the  roots  of  plants  slow  to  adapt  themselves  would 
be  fatal  to  their  existence. 

Nobbe  has,  however,  carefully  compared  the  roots  of 
buckwheat,  as  developed  in  the  soil,  with  those  emitted 
in  water,  without  being  able  to  observe  any  structural 
differences.  The  facts  above  detailed  admit  of  partial,  if 
not  complete,  explanation,  without  recourse  to  the  suppo- 
sition that  soil-  and  water-roots  are  essentially  diverse  in 
nature.  When  a  plant  which  is  rooted  in  the  soil  ia 
taken  up  so  that  the  fibrils  are  not  broken  or  injured, 
and  set  into  water,  it  does  not  suffer  any  hindrance  in 
growth,  as  Sachs  found  by  his  later  experiments.  (Ex- 
perimental Physiologic,  p.  177.)  Ordinarily,  the  suspen- 
sion of  growth  and  decay  of  fibrils  and  rootlets  is  due, 
doubtless,  to  the  mechanical  injury  they  suffer  in  remov- 
ing from  the  soil.  Again,  when  a  plant  that  has  been 
reared  in  water  is  planted  in  earth,  similar  injury  occurs 
in  packing  the  soil  about  the  roots,  and  moreover  the 
fibrils  cannot  be  brought  into  that  close  contact  with  the 
soil  which  is  necessary  for  them  to  supply  the  foliage 
with  water  ;  hence  the  plant  wilts,  and  may  easily  perish 


280  HOW  CROPS  GROW. 

unless  profusely  watered  or  shielded  from  evaporation. 

The  air-roots  of  Orchids,  which  never  reach  the  soil, 
have  a  peculiar  spongy  texture  and  take  up  the  water 
which  exists  as  vapor  in  the  air,  as  shown  by  the  experi- 
ments of  linger,  Chatin,  and  Sachs.  Duchartre's  inves- 
tigations led  him  to  deny  their  absorptive  power.  (Ele- 
ments de  Botanique,  p.  216.)  In  his  experiments  made 
on  entire  plants,  the  air-roots  failed  to  make  good  the 
loss  by  evaporation  from  the  other  parts  of  the  plant. 

It  is  evident  from  common  observation  that  moisture 
is  the  condition  that  chiefly  determines  root-develop- 
ment. Not  only  do  all  seeds  sprout  and  send  forth  roots 
when  provided  with  abundant  moisture  at  suitable  tem- 
peratures, but  generally  older  roots  and  stems,  and 
fleshy  leaves,  or  cuttings  from  these,  will  produce  new 
rootlets  when  properly  circumstanced  as  regards  moisture, 
whether  that  moisture  be  supplied  by  aid  of  a  covering 
of  damp  soil,  wet  sand  or  paper,  by  stationing  in  humid 
air,  or  by  immersion  in  water  itself. 

Root-Excretions. — It  was  formerly  supposed  that 
the  roots  of  plants  perform  a  function  of  excretion,  the 
reverse  of  absorption — that  plants,  like  animals,  reject 
matters  which  are  no  longer  of  use  in  their  organism, 
and  that  the  rejected  matters  are  poisonous  to  the  kind 
of  vegetation  from  which  they  originated.  De  Candolle, 
an  eminent  French  botanist,  who  first  advanced  this  doc- 
trine, founded  it  upon  the  observation  that  certain  plants 
exude  drops  of  liquid  from  their  roots  when  these  are 
placed  in  dry  sand,  and  that  odors  exhale  from  the  roots 
of  other  plants.  Numerous  experiments  have  been  in- 
stituted at  various  times  for  the  purpose  of  testing  this 
question.  Noteworthy  are  those  of  Dr.  Alfred  Gyde 
(Trans.  Highland  and  Agr.  Soc.,  1845-47,  pp.  273-92). 
This  experimenter  planted  a  variety  of  agricultural  plants, 
viz.,  wheat,  barley,  oats,  rye,  beans,  peas,  vetches,  cab- 
bage, mustard,  and  turnips,  in  pots  filled  either  with 


VEGETATIVE  ORGANS  OF  PLANTS.  281 

garden  soil,  sand,  moss,  or  charcoal,  and  after  they  had 
attained  considerable  growth,  removed  the  earth,  etc., 
from  their  roots  by  washing  with  water,  using  care  not 
to  injure  or  wound  them,  and  then  immersed  the  roots 
in  vessels  of  pure  water.  The  plants  were  allowed  to  re- 
main in  these  circumstances,  their  roots  being  kept  in 
darkness,  but  their  foliage  exposed  to  light,  from  three 
to  seventeen  days.  In  most  cases  they  continued  appa- 
rently in  a  good  state  of  health.  At  the  expiration  of 
the  time  of  experiment,  the  water  which  had  been  in 
contact  with  the  roots  was  evaporated,  and  was  found  to 
leave  a  very  minute  amount  of  yellowish  or  brown  mat- 
ter, a  portion  of  which  was  of  organic  and  the  remainder 
of  mineral  origin.  Dr.  Gyde  concluded  that  plants  do 
throw  off  organic  and  inorganic  excretions  similar  in 
composition  to  their  sap  ;  but  that  the  quantity  is  ex- 
ceedingly small,  and  is  not  injurious  to  the  plants  which 
furnish  them. 

In  the  light  of  newer  investigations  touching  the 
structure  of  roots  and  their  adaptation  to  the  medium 
which  happens  to  invest  them,  we  may  well  doubt 
whether  agricultural  plants  in  the  healthy  state  excrete 
any  solid  or  liquid  matters  whatever  from  their  roots. 
The  familiar  excretion  of  gum,  resin,  and  sugar*  from 
the  stems  of  trees  appears  to  result  from  wounds  or  dis- 
ease, and  the  matters  which  in  the  experiments  of  Gyde 
and  others  were  observed  to  be  communicated  by  the 
roots  of  plants  to  pure  water  probably  came  either  from 
the  continual  pushing  off  of  the  tips  of  the  rootlets  by 
the  interior  growing  point — a  process  always  naturally 
accompanying  the  growth  of  roots — or  from  the  disor- 
ganization of  the  absorbent  root-hairs. 

Under  certain  circumstances,  small  quantities  of  sol- 
uble salts  or  free  acids  may  indeed  diffuse  out  of  the 

•From  the  wounded  bark  of  the  sugar-pine  (Pinus  Lambertiana)  of 
California. 


283  HOW  CROPS  GROW. 

root-cells  into  the  water  of  the  soil.  This  is,  however, 
no  physiological  action,  but  a  purely  physical  process. 

Vitality  of  Roots. — It  appears  that  in  case  of  most 
plants  the  roots  cannot  long  continue  their  vitality  if 
their  connection  with  the  leaves  be  interrupted,  unless, 
indeed,  they  be  kept  at  a  winter  temperature.  Hence 
weeds  may  be  effectually  destroyed  by  cutting  down 
their  tops;  although,  in  many  cases,  the  process  must 
be  several  times  repeated  before  the  result  is  attained. 

The  roots  of  our  root-crops,  properly  so-called,  viz., 
beets,  turnips,  carrots,  and  parsnips,  when  harvested  in 
autumn,  contain  the  elements  of  a  second  year's  growth 
of  stem,  etc.,  in  the  form  of  a  bud  at  the  crown  of  the 
root.  If  the  crown  be  cut  away  from  the  root,  the  latter 
cannot  vegetate,  while  the  growth  of  the  crown  itself  is 
not  thereby  prevented. 

As  regards  internal  structure,  the  root  closely  resem- 
bles the  stem,  and  what  is  stated  of  the  latter,  on  subse- 
quent pages,  applies  in  all  essential  points  to  the  former. 

§  2. 

THE  STEM. 

Shortly  after  the  protrusion  of  the  rootlet  from  a  ger- 
minating seed,  the  STEM  makes  its  appearance.  It  has, 
in  general,  an  upward  direction,  which  in  many  plants 
is  permanent,  while  in  others  it  shortly  falls  to  the 
ground  and  grows  thereafter  horizontally. 

All  plants  of  the  higher  orders  have  stems,  though  in 
many  instances  they  do  not  appear  above  ground,  but 
extend  beneath  the  surface  of  the  soil,  and  are  usually 
considered  to  be  roots. 

While  the  root,  save  in  exceptional  cases,  does  not 
develop  other  organs,  it  is  the  special  function  of  the 
gtem  to  bear  the  leaves,  flowers,  and  seed  of  the  plant, 


VEGETATIVE  ORGANS  OF  PLANTS. 


283 


and  even  in  certain  tribes  of  vegetation,  like  the  cacti, 
which  have  no  leaves,  to  perform  the  offices  of  these 
organs.  In  general,  the  functions  of  the  stem  are  sub- 
ordinate to  those  of  the  organs  which  it  bears — the  leaves 
and  flowers.  It  is  the  support  of  these  organs,  and,  it 
would  appear,  only  extends  in  length  or  thickness  with 
the  purpose  of  sustaining  them  mechanically  or  provid- 
ing them  with  nutriment. 

Buds. — In  the  seed  the  stem  exists  in  a  rudimentary 
state,  associated  with  undeveloped  leaves,  forming  a  bud. 
The  stem  always  proceeds  at  first  from  a  bud,  during  all 
its  growth  is  terminated  by  a  bud  at  every  growing  point, 
and  only  ceases  to  be  thus  tipped  when  it  fully  accom- 
plishes its  growth  by  the  production  of  seed,  or  dies 
from  injury  or  disease. 

In  the  leaf-bud  we  find  a  number  of  embryo  leaves 
and  leaf -like  scales,  in  close  contact  and  within  each 
other,  but  all  at- 
tached at  the  base 
to  a  central  conical 
axis,  Fig.  45.  The 
opening  of  the  bud 
consists  in  the 
lengthening  of  this 
axis,  which  is  the 
stem,  and  the  con- 
sequent separation 
from  each  other  as 

well  as  expansion  of  Pig.  45. 

the  leaves.     If  the 

rudimentary  leaves  of  a  bud  be  represented  by  a  nest  of 
flower-pots,  the  smaller  placed  within  the  larger,  the 
stem  may  be  signified  by  a  rope  of  India-rubber  passed 
through  the  holes  in  the  bottom  of  the  pots.  The 
growth  of  the  stem  may  now  be  shown  by  stretching  the 
rope,  whereby  the  pots  are  brought  away  from  each 


384  HOW  CROPS  GROW. 

other,  and  the  whole  combination  is  made  to  assume  the 
character  of  a  fully-developed  stem,  -bearing  its  leaves  at 
regular  intervals ;  with  these  important  differences,  that 
the  portions  of  stem  nearest  the  root  extend  more  rap- 
idly than  those  above  them,  and  the  stem  has  within  it 
the  material  and  the  mechanism  for  the  continual  for- 
mation of  new  buds,  which  unfold  in  successive  order. 

In  Fig.  45,  which  represents  the  two  terminal  buds  of 
a  lilac  twig,  is  shown  not  only  the  external  appearance 
of  the  buds,  which  are  covered  with  leaf-like  scales, 
imbricated  like  shingles  on  a  roof ;  but,  in  the  section, 
are  seen  the  edges  of  the  undeveloped  leaves  attached  to 
the  conical  axis.  All  the  leaves  and  the  whole  stem  of 
a  twig  of  one  summer's  growth  thus  exist  in  the  bud,  in 
plan  and  in  miniature.  Subsequent  growth  is  but  the 
development  of  the  plan. 

In  the  flower-bud  the  same  structure  is  manifest,  save 
that  the  rudimentary  flowers  and  fruit  are  enclosed 
within  the  leaves,  and  may  often  be  seen  plainly  on  cut- 
ting the  bud  open. 

Nodes;  Internodes. — Nodes  are  those  knots  or  parts 
of  the  stem  where  the  leaves  are  attached.  The  portions 
of  the  stem  between  the  nodes  are  termed  internodes. 
It  is  from  the  nodes  that  roots  most  freely  develop  when 
stems  (layers  or  cuttings)  are  surrounded  by  moist  air  or 
soil. 

Culms. — The  grasses  and  the  common  cereal  grains 
have  single,  unbranched  stems,  termed  culms  in  botani- 
cal language.  The  leaves  of  these  plants  clasp  the  stem 
entirely  at  their  base,  and  rest  upon  a  well-defined,  thick- 
ened node. 

Branching  Stems — Other  agricultural  plants  besides 
those  just  mentioned,  and  all  the  trees  of  temperate  cli- 
mates, have  branching  stems.  As  the  principal  or  main 
stem  elongates,  so  that  the  leaves  arranged  upon  it  sepa- 
rate from  each  other,  we  find  one  or  more  buds  at  the 


VEGETATIVE  ORGANS  OF   PLANTS.  285 

point  where  the  base  of  the  leaf  or  of  the  leaf-stalk 
unites  with  the  stem.  From  these  axillary  buds,  in  case 
their  growth  is  not  checked,  side-stems  or  branches 
issue,  which  again  subdivide  in  the  same  manner  into 
branc  hlets. 

In  perennial  plants,  when  young,  or  in  their  young 
ehoots,  it  is  easy  to  trace  the  nodes  and  interned es,  or 
the  points  where  the  leaves  are  attached  and  the  inter- 
vening spaces,  even  for  some  time  after  the  leaves,  which 
only  endure  for  one  year,  are  fallen  away.  The  nodes 
are  manifest  by  the  enlargement  of  the  stem,  or  by  the 
scar,  covered  with  corky  matter,  which  marks  the  spot 
where  the  leaf-stalk  was  attached.  As  the  stem  grows 
older  these  indications  of  its  early  development  are  grad- 
ually obliterated. 

In  a  forest  where  the  trees  are  thickly  crowded,  the 
lower  branches  die  away  from  want  of  light;  the  scars 
resulting  from  their  removal,  or  short  stumps  of  the 
limbs  themselves,  are  covered  with  a  new  growth  of 
wood,  so  that  the  trunk  finally  appears  as  if  it  had  always 
been  destitute  of  branches,  to  a  great  height. 

When  all  the  buds  develop  normally  and  in  due  pro- 
portion, the  plant,  thus  regularly  built  up,  has  a  sym- 
metrical appearance,  as  frequently  happens  with  many 
herbs,  and  also  with  some  of  the  cone-bearing  trees, 
especially  the  balsam-fir. 

Latent  Buds. — Often,  however,  many  of  the  buds 
remain  undeveloped,  either  permanently  or  for  a  time. 
Many  of  the  side-buds  of  most  of  our  forest  and  fruit 
trees  fail  entirely  to  grow,  while  others  make  BO  progress 
until  the  summer  succeeding  their  first  appearance. 
When  the  active  buds  are  destroyed,  either  by  frosts  or 
by  pinching  off,  other  buds  that  would  else  remain 
latent  are  pushed  into  growth.  In  this  way  trees 
whose  young  leaves  are  destroyed  by  spring  frosts  cover 
themselves  again,  after  a  time,  with  foliage.  In  this  way, 


286  HOW   CROPS   GROW. 

too,  the  gardener  molds  a  straggling,  ill-shaped  shrub  or 
plant  into  almost  any  form  he  chooses ;  for,  by  removing 
branches  and  buds  where  they  have  grown  in  undue  pro- 
portion, he  not  only  checks  excess,  but  also  calls  forth 
development  in  the  parts  before  suppressed.  Close 
priming  or  breaking  the  young  twigs  causes  abundant 
development  of  flower-buds  on  fruit  trees  that  otherwise 
"run  to  wood." 

Adventitious  or  irregular  Buds  are  produced  from 
the  stems  as  well  as  older  roots  of  many  plants,  when 
they  are  mechanically  injured  during  the  growing  season. 
The  soft  or  red  maple  and  the  chestnut,  when  cut  down, 
habitually  throw  out  buds  and  new  stems  from  the 
stump,  and  the  basket-willow  is  annually  polled,  or  pol- 
larded, to  induce  the  growth  of  slender  shoots  from  an 
old  trunk. 

Elongation  of  Stems. — While  roots  extend  chiefly 
at  their  extremities,  we  find  the  stem  elongates  equally, 
or  nearly  so,  in  all  its  contiguous  parts,  as  is  manifest 
from  what  has  already  been  stated  in  illustration  of  its 
development  from  the  bud. 

Besides  the  upright  stem,  there  are  a  variety  of  pros- 
trate and  in  part  subterranean  stems,  which  may  be 
briefly  noticed. 

Runners  and  Layers  are  stems  that  are  sent  out  hor- 
izontally just  above  the  soil,  and,  coming  in  contact  with 
the  earth,  take  root,  forming  new  plants,  which  may 
thenceforward  grow  independently.  The  gardener  takes 
advantage  of  these  stems  to  propagate  certain  plants. 
The  strawberry  furnishes  the  most  familiar  example  of 
runners,  while  many  of  the  young  shoots  of  the  currant 
fall  to  the  ground  and  become  layers.  The  runner  is  a 
somewhat  peculiar  stem.  It  issues  horizontally,  and 
usually  bears  but  few  or  no  leaves.  The  layer  does  not 
differ  from  an  ordinary  stem,  except  by  the  circum- 
stance, often  accidental,  of  becoming  prostrate.  Many 


VEGETATIVE  ORGANS  OF  PLANTS.  287 

plants  which  usually  send  out  no  layers  are  nevertheless 
artificially  layered  by  bending  their  stems  or  branches  to 
the  ground,  or  by  attaching  to  them  a  ball  or  pot  of 
earth.  The  striking  out  of  roots  from  the  layer  is  in 
many  cases  facilitated  by  cutting  half  through,  twisting, 
or  otherwise  wounding  the  stem  at  the  point  where  it  is 
buried  in  the  soil. 

The  tillering  of  wheat  and  other  cereals,  and  of  many 
grasses,  is  the  spreading  of  the  plant  by  layers.  The  first 
stems  that  appear  from  these  plants  ascend  vertically, 
but,  subsequently,  other  stems  issue,  whose  growth  is, 
for  a  time,  nearly  horizontal.  They  thus  come  in  con- 
tact with  the  soil,  and  emit  roots  from  their  lower  joints. 
From  these  again  grow  new  stems  and  new  roots  in  rapid 
succession,  so  that  a  stool  produced  from  a  single  kernel 
of  winter  wheat,  having  perfect  freedom  of  growth,  has 
been  known  to  carry  50  or  60  grain-bearing  culms. 
(Hallet,  Jour.  Roy.  Soc.  of  Eng.,  22,  p.  372.) 

Suckers. — When  branches  ariso  from  the  stem  below 
the  surface  of  the  soil,  so  that  they  are  partly  subter- 
ranean and  partly  aerial,  as  in  the  Rose  and  Raspberry, 
they  are  termed  Suckers.  These  leafy  shoots  put  out 
roots  from  their  buried  nodes,  and  may  be  separated 
artificially  and  used  for  propagating  the  plant. 

Subterranean  Stems. — Of  these  there  are  three 
forms.  They  are  usually  taken  to  be  roots,  from  the 
fact  of  existing  below  the  surface  of  the  soil.  This  cir- 
cumstance is,  however,  quite  accidental.  The  pods  of 
the  peanut  (Arachis  hypogoea)  ripen  beneath  the 
ground — the  flower-stems  lengthening  and  penetrating 
the  earth  as  soon  as  the  blossom  falls ;  but  these  stems 
are  not  by  any  means  to  be  confounded  with  roots. 

Root-stocks,  or  Rhizomes. — True  roots  are  desti- 
tute of  leaves.  This  fact  easily  distinguishes  them  from 
the  rhizome,  which  is  a  stem  that  extends  below  the  sur- 
face of  the  ground.  At  the  nodes  of  these  root-stocks, 


288 


HOW  CROPS  GROW. 


as  they  are  appropriately  named,  scales  or  rudimentary 
leaves  are  seen,  and  thence  roots  proper  are  emitted.  In 
the  axils  of  the  scales  may  be  traced  the  buds  from  which 
aerial  and  fruit-bearing  stems  proceed.  Examples  of 
the  root-stock  are  very  common.  Among  them  we  may 
mention  the  blood-root  and  pepper-root  as  abundant  in 
the  woods  of  the  Northern  and  Middle  States,  various 
mints,  asparagus,  and  the  quack-grass  (Agropyrum* 
repens)  represented  in  Fig.  46,  which  infests  so  many 
farms.  Each  node  of  the  root-stock,  being  usually  sup- 
plied with  roots,  and  having  latent  buds,  is  ready  to 
become  an  independent  growth  the  moment  it  is  detached 


Fig.  46. 


from  its  parent  plant.  In  this  way  quack-grass  becomes 
especially  troublesome,  for  the  more  the  fields  where  it 
has  obtained  a  footing  are  tilled  the  more  does  it  com- 
monly spread  and  multiply;  only  oft-repeated  harrow- 
ing in  a  season  of  prolonged  dryness  suffices  for  its 
extirpation. 

Corms  are  enlargements  of  the  base  of  the  stem,  bear- 
ing leaf -buds  either  at  the  summit  or  side,  and  may  be 
regarded  as  much-shortened  rhizomes,  with  only  a  few 
Blightly-developed  internodes.  Externally  they  resemble 
bulbs.  The  garden  crocus  furnishes  an  example. 

Tubers  of  many  plants  are  fleshy  enlargements  of  the 

•Formerly  Triticwn, 


VEGETATIVE   ORGANS  OP  PLANTS.  289 

extremities  of  subterranean  stems.  Their  eyes  are  the 
points  where  the  buds  exist,  usually  three  together, 
and  where  minute  scales — rudimentary  leaves — 'may  be 
observed.  The  common  potato  and  artichoke  (HeUan- 
thus  tuberosus)  are  instances  of  this  kind  of  tubers. 
Tubers  serve  excellently  for  propagation.  Each  eye,  or 
bud,  may  become  a  new  plant.  From  the  quantity  of 
starch,  etc.,  accumulated  in  them,  they  are  of  great 
importance  as  food.  The  number  of  tubers  produced  by 
a  potato-plant  appears  to  be  increased  by  planting  orig- 
inally at  a  considerable  depth,  or  by  "hilling  up"  earth 
around  the  base  of  the  aerial  stems  during  the  early 
stages  of  its  growth. 

Bulbs  are  greatly  thickened  stems,  whose  leaves — • 
usually  having  the  form  of  fleshy  scales  or  concentric  coats 
— are  in  close  contact  with  each  other,  and  arise  from 
nearly  a  common  base,  the  internodes  being  undeveloped. 
The  bulb  is,  in  fact,  a  permanent  bud,  usually  in  part 
or  entirely  subterranean.  From  its  apex,  the  proper 
stem,  the  foliage,  etc.,  proceed;  while  from  its  base 
roots  are  sent  out.  The  structural  identity  of  the  bulb 
with  a  bud  is  shown  by  the  fact  that  the  onion,  which 
furnishes  the  commonest  example  of  the  bulb,  often 
bears  bulblets  at  the  top  of  its  stem,  in  place  of  flowers. 
In  like  manner,  the  axillary  buds  of  the  tiger-lily  are 
thickened  and  fleshy,  and  fall  off  as  bulblets  to  the 
ground,  where  they  produce  new  plants. 

STRUCTURE  OF  THE  STEM. — The  stem  is  so  compli- 
cated that  to  discuss  it  fully  would  occupy  a  volume. 
For  our  immediate  purposes  it  is,  however,  only  neces- 
sary to  notice  its  structural  composition  very  concisely. 

The  rudimentary  stem,  as  found  in  the  seed,  or  the 
new-formed  part  of  the  maturer  stem  at  the  growing 
points  just  below  the  terminal  buds,  consists  of  cellular 
tissue,  or  is  an  aggregate  of  rounded  and  cohering  cells, 
which  rapidly  multiply  during  the  vigorous  growth  of 
the  plant.  Id 


290  HOW  CROPS  GROW. 

In  some  of  the  lower  orders  of  vegetation,  as  in  mush, 
rooms  and  lichens,  the  stem,  if  any  exist,  always  pre- 
serves a'  purely  cellular  character ;  but  in  all  flowering 
plants  the  original  cellular  tissue  of  the  stem,  as  well  as 
of  the  root,  is  shortly  penetrated  by  vascular  tissue, 
consisting  of  ducts  or  tubes,  which  result  from  the 
obliteration  of  the  horizontal  partitions  of  cell-tissue, 
and  by  wood-cells,  which  are  many  times  longer  than 
wide,  and  the  walls  of  which  are  much  thickened  by 
internal  deposition. 

These  ducts  and  wood-cells,  together  with  some  other 
forms  of  cells,  are  usually  found  in  close  connection,  and 
are  arranged  in  bundles,  which  constitute  the  fibers  of 
the  stem.  They  are  always  disposed  lengthwise  in  the 
stem  and  branches.  They  are  found  to  some  extent  in 
the  softest  herbaceous  stems,  while  they  constitute  a 
large  share  of  the  trunks  of  most  shrubs  and  trees. 
From  the  toughness  which  they  possess,  and  the  manner 
in  which  they  are  woven  through  the  original  cellular 
tissue,  they  give  to  the  stem  its  solidity  and  strength. 

Flowering  plants  may  be  divided  into  two  great  classes, 
in  consequence  of  important  and  obvious  differences  in 
the  structure  of  their  stems  and  seeds.  These  are :  1, 
Monocotyledons,  or  Endogens  ;  and  2,  Dicotyledons,  or  Exo- 
gens.  As  regards  their  stems,  these  two  classes  of  plants 
differ  in  the  arrangement  of  the  vascular  or  woody  tissue. 

Endogenous  Plants  are  those  whose  stems  enlarge  by 
the  formation  of  new  wood  in  the  interior,  and  not  by 
the  external  growth  of  concentric  layers.  The  embryos 
in  the  seeds  of  endogenous  plants  consist  of  a  single  piece 
— do  not  readily  split  into  halves — or,  in  botanical  lan- 
guage, have  but  one  cotyledon;  hence  are  called  monoco- 
tyledonous.  Indian  corn,  sugar-cane,  sorghum,  wheat, 
oats,  rye,  barley, '  the  onion,  asparagus,  and  all  the 
grasses,  belong  to  this  tribe  of  plants. 

If  a  stalk  of  maize,  asparagus,  or  bamboo  be  cut 


VEGETATIVE  ORGANS  OF  PLANTS.  291 

across,  the  fiber-like  bundles  of  ducts  and  wood-cells  are 
seen  disposed  somewhat  uniformly  throughout  the  sec- 
tion, though  less  abundantly  towards  the  center.  On 
splitting  the  fresh  stalk  lengthwise,  these  vascular  bun- 
dies  may  be  torn  out  like  strings.  At  the  nodes,  where 
the  stem  is  branched,  or  where  leaf-stalks  are  attached, 
the  vascular  bundles  likewise  divide  and  form  a  net-work. 
In  a  ripe  maize-stalk  which  is  exposed  to  circumstances 
favoring  decay,  the  soft  cell-tissue  first  suffers  change 
and  often"  quite  disappears,  leaving  the  firmer  vascular 
bundles  unaltered  in  form.  A  portion  of  the  base  of 
such  a  stalk,  cut  lengthwise,  is  represented  in  Fig.  47, 
where  the  vascular  bundles  are  seen  arranged  parallel  to 
each  other  in  the  internodes,  and  curiously  interwoven 
and  branched  at  the  nodes,  both  at  those  (a  and  6)  from 
which  roots  issued,  or  at  that  (c)  which  was  clasped  by 
the  base  of  a  leaf. 

The  endogenous  stem,  as  represented  in  the  maize- 
stalk,  has  no  well-defined  bark  that  admits  of  being 


stripped  off  externally,  and  no  separate  central  pith  of 
soft  cell-tissue  free  from  vascular  bundles.  It,  like  the 
aerial  portions  of  all  flowering  plants,  is  covered  with  a 
skin,  or  epidermis,  composed  usually  of  one  or  several 
layers  of  flattened  cells,  whose  walls  are  thick,  and  far 
less  penetrable  to  fluid  than  the  delicate  texture  of  the 
interior  cell-tissue.  The  stem  is  denser  and  harder  at 
the  circumference  than  towards  the  center.  This  is  due 
to  the  fact  that  the  bundles  are  more  numerous  and 
older  towards  the  outside  of  the  stem.  The  newer  bun- 
dles, as  they  continually  form  at  the  base  of  the  growing 
terminal  bud,  pass  to  the  inside  of  the  stem,  an4  after- 


292 


HOW  CROPS  GROW. 


wards  outwards  and  downwards,  and  hence  the  designa- 
tion endogenous,  which  in  plain  English  means  inside- 
grower. 

In  consequence  of  this  inner  growth,  the  stems  of 
most  woody  endogens,  as  the  palms,  after  a  time  become 
so  indurated  externally  that  all  lateral  expansion  ceases, 
and  the  stem  increases  only  in  height.  In  some  cases, 
the  tree  dies  because  its  interior  is  so  closely  packed  with 


Fig.  4& 

bundles  that  the  descent  of  new  ones,  and  the  accom- 
panying vital  processes,  become  impossible. 

In   herbaceous  endogens  the    soft   stem  admits  the 
indefinite  growth  of  new  vascular  tissue. 


VEGETATIVE  ORGANS  OP  PLANTS. 


293 


The  stems  of  the  grasses  are  hollow,  except  at  the 
nodes.  Those  of  the  rushes  have  a  central  pith  free  from 
vascular  tissue. 

The  Minute  Structure  of  the  Endogenous  Stem 
is  exhibited  in  the  accompanying  cuts,  which  represent 
highly  magnified  sections  of  a  Vascular  Bundle  or  fiber 
from  the  maize-stalk.  As  before  remarked,  the  stem  is 
composed  of  a  groundwork  of  delicate  cell-tissue,  in 
which  bundles  of  vascular-tissue  are  distributed.  Fig. 
48  represents  a  cross  section  of  one  of  these  bundles,  c, 
g,  h,  as  well  as  of  a  portion  of  the  surrounding  cell-tis- 


Fig.  49. 

sue,  a,  a.  The  latter  consists  of  quite  large  cells,  which 
have  between  them  considerable  inter-cellular  spaces,  i. 
The  vascular  bundle  itself  is  composed  externally  of 
narrow,  thick-walled  cells,  of  which  those  nearest  the 
exterior  of  the  stem,  h,  are  termed  bast-cells,  as  they 
correspond  in  character  and  position  to  the  cells  of  the 
bast  or  inner  bark  of  our  common  trees ;  those  nearest 
the  center  of  the  stem,  c,  are  wood-cells.  In  the  maize 
stem,  bast-cells  and  wood-cells  are  quite  alike,  and  are 


294  HOW  CROPS  GROW. 

distinguished  only  by  their  position.  In  other  plants, 
they  are  often  unlike  as  regards  length,  thickness,  and 
pliability,  though  still,  for  the  most  part,  similar  in 
form.  Among  the  wood-cells  we  observe  a  number  of 
ducts,  d,  e,  f,  and  between  these  and  the  bast-cells  is  a 
delicate  and  transparent  tissue,  g,  which  is  the  cambium, 
in  which  all  the  growth  of  the  bundle  goes  on  until  it 
is  complete.  On  either  hand  is  seen  a  remarkably  large 
duct,  b,  b,  while  the  residue  of  the  bundle  is  composed 
of  long  and  rather  thick-walled  wood-cells. 

Fig.  49  represents  a  section  made  vertically  through 
the  bundle  from  c  to  li.  In  this  the  letters  refer  to  the 
same  parts  as  in  the  former  cut :  a,  a  is  the  cell-tissue, 
enveloping  the  vascular  bundle;  the  cells  are  observed 
to  be  much  longer  than  wide,  but  are  separated  from 
each  other  at  the  ends  as  well  as  sides  by  an  imperforate 
membrane.  The  wood  and  bast-cells,  c,  h,  are  seen  to 
be  long,  narrow,  thick-walled  cells  running  obliquely  to 
a  point  at  either  end.  The  wood-cells  of  oak,  hickory, 
and  the  toughest  woods,  as  well  as  the  bast-cells  of  flax 
nnd  hemp,  are  quite  similar  in  form  and  appearance. 
The  proper  ducts  of  the  stem  are  next  in  the  order  of 
our  section.  Of  these  there  are  several  varieties,  as  ring- 
ducts,  d;  spiral  ducts,  e;  dotted  ducts,  f.  These  are 
continuous  tubes  produced  by  the  absorption  of  the 
transverse  membranes  that  once  divided  them  into  such 
cells  as  a,  a,  and  they  are  thickened  internally  by  ring- 
like,  spiral,  or  punctate  depositions  of  cellulose  (see  Fig. 
32,  p.  248).  Wood  or  bast-cells  that  consist  mainly  of 
cellulose  are  pliant  and  elastic.  It  is  the  deposition  of 
other  matters  (so-called  ligniri)  in  their  walls  which  ren- 
ders them  stiff  and  brittle. 

At  g,  the  cambial  tissue  is  observed  to  consist  of  del- 
icate cylindrical  cells.  Among  these,  partial  absorption 
of  the  separating  membrane  often  occurs,  so  that  they 
communicate  directly  with  each  other  through  sieve-like 


VEGETATIVE  ORGANS  OF  PLANTS. 


295 


partitions,  and  become  continuous  channels  or  ducts. 
(Sieve-cells,  p.  303. )  The  cambium  is  the  seat  of  growth 
by  cell-formation.  Accordingly,  when  a  vascular  bun- 
dle has  attained  maturity,  it  no  longer  possesses  a  cam- 
bium. 

To  complete  our  view  of  the  vascular  bundle,  Fig.  50 
represents  a  vertical  section  made  at  right  angles  to  the 
last,  cutting  two  large  ducts,  b,  b;  a,  a  is  cell- tissue; 
c 


Fig.  50. 


c,  c  are  bast  or  wood-cells  less  thickened  by  interior 
deposition  than  those  of  Fig.  49 ;  d  is  a  ring  and  spiral 
duct ;  b,  b  are  large  dotted  ducts,  which  exhibit  at  g,  g 
the  places  where  they  were  once  crossed  by  the  double 
membrane  composing  the  ends  of  two  adhering  cells,  by 
whose  absorption  and  removal  an  uninterrupted  tube 
has  been  formed.  In  these  large  dotted  ducts  there 
appears  to  be  no  direct  communication  with  the  sur- 
rounding cells  through  their  sides.  The  dots  or  pits 
are  simply  very  thin  points  in  the  cell-wall,  through 
which  sap  may  soak  or  diffuse  laterally,  but  not  flow. 


296  HOW  CROPS  GROW. 

When  the  cells  become  mature  and  cease  growth,  the 
pits  often  become  pores  by  absorption  of  the  membrane, 
so  that  the  ducts  thus  enter  into  direct  communication 
with  each  other. 

Exogenous  Plants  are  those  whose  stems  contin- 
ually enlarge  in  diameter  by  the  formation  of  new  tissue 
near  the  outside  of  the  stem.  They  are  outside-growers. 
Their  seeds  are  usually  made  up  of  two  loosely-united 
parts,  or  cotyledons,  wherefore  they  are  designated 
dicotyledonous.  All  the  forest  trees  of  temperate  cli- 
mates, and,  among  agricultural  plants,  the  bean,  pea, 
clover,  potato,  beet,  turnip,  flax,  etc.,  are  exogens. 

In  the  exogenous  stem  the  bundles  of  ducts  and  fibers 
that  appear  in  the  cell-tissue  are  always  formed  just 
within  the  rind.  They  occur  at  first  separately,  as  in 
the  endogens,  but,  instead  of  being  scattered  throughout 
the  cell-tissue,  are  disposed  in  a  circle.  As  they  grow, 
they  usually  close  up  to  a  ring  or  zone  of  wood,  which 
incloses  unaltered  cell-tissue — the  pith. 

A$  the  stem  enlarges,  new  rings  of  fibers  may  be 
formed,  but  always  outside  the  older  ones.  In  hard 
stems  of  slow  growth  the  rings  are  close  together  and 
chiefly  consist  of  very  firm  wood-cells.  In  the  soft  stems 
of  herbs  the  cellular  tissue  preponderates,  and  the  ducts 
and  cells  of  the  vascular  zones  are  delicate.  The  harden- 
ing of  herbaceous  stems  which  takes  place  as  they  become 
mature  is  due  to  the  increase  and  induration  of  the 
wood-cells  and  ducts. 

The  circular  disposition  of  the  fibers  in  the  exogenous 
*stem  may  be  readily  seen  in  a  multitude  of  common 
plants. 

The  potato  tuber  is  a  form  of  stem  always  accessible 
for  observation.  If  a  potato  be  cut  across  near  the  stem- 
end  with  a  sharp  knife,  it  is  usually  easy  to  identify  upon 
the  section  a  ring  of  vascular-tissue,  the  general  course 
of  which  is  parallel  to  the  circumference  of  the  tuber 


VEGETATIVE   ORGANS   OF   PLANTS.  297 

except  where  it  runs  out  to  the  surface  in  the  eyes  or 
buds,  and  in  the  narrow  stem  at  whose  extremity  it 
grows.  If  a  slice  across  a  potato  be  soaked  in  solution 
of  iodine  for  a  few  minutes,  the  vascular  ring  becomes 
strikingly  apparent.  In  its  active  cambial  cells,  albu- 
minoids are  abundant,  which  assume  a  yellow  tinge  with 
iodine.  The  starch  of  the  cell-tissue,  on  the  other  hand, 
becomes  intensely  blue,  making  the  vascular  tissue  all 
the  more  evident. 

Since  the  structure  of  the  root  is  quite  similar  to  that 
of  the  stem,  a  section  of  the  common  beet  as  well  as  one 
of  a  branch  from  any  tree  of  temperate  latitudes  may 
serve  to  illustrate  the  concentric  arrangement  of  the  vas- 
cular zones  when  they  are  multipled  in  number. 

Pith  is  the  cell-tissue  of  the  center  of  the  stem.  In 
young  stems  it  is  charged  with  juices ;  in  older  ones  it 
often  becomes  dead  and  sapless.  In  many  cases,  espec- 
ially when  growth  is  active,  it  becomes  broken  and  nearly 
obliterated,  leaving  a  hollow  stem,  as  in  a  rank  pea-vine, 
or  clover-stalk,  or  in  a  hollow  potato.  In  the  potato 
tuber  the  pith-cells  are  occupied  throughout  with  starch, 
although,  as  the  coloration  by  iodine  makes  evident,  the 
quantity  of  starch  diminishes  from  the  vascular  zone 
towards  the  center  of  the  tuber. 

The  Rind,  which,  at  first,  consists  of  mere  epidermis, 
or  short,  thick-walled  cells,  overlying  soft  cellular  tissue, 
becomes  penetrated  with  cells  of  unusual  length  and 
tenacity,  %which,  from  their  position  in  the  plant,  are 
termed  bast-cells.  These,  together  with  ducts  of  various 
kinds,  constitute  the  so-called  bast,  which  grows  chiefly 
upon  the  interior  of  the  rind,  in  successive  annual  layers, 
in  close  proximity  to  the  wood.  "With  their  abundant 
development  and  with  age,  the  rind  becomes  bark  as  it 
occurs  on  shrubs  and  trees.  The  bast-cells  give  to  the 
bark  its  peculiar  toughness,  and  cause  ;t  to  come  off  the 
Stem  in  long  and  pliant  strips. 


298  HOW  CHOPS  GROW. 

All  the  vegetable  textile  materials  employed  in  the  man- 
ufacture of  cloth  and  cordage,  with  the  exception  of  cot- 
ton, as  flax,  hemp,  New  Zealand  flax,  etc.,  are  bast-fibers- 
(See  p.  248.) 

In  some  plants  the  annual  layers  of  bast  are  so  sepa- 
rated by  cellular  tissue  that  in  old  stems  they  may  be 
split  from  one  another.  Various  kinds  of  matting  are 
made  by  weaving  together  strips  of  bast  layers,  especially 
those  of  the  Linden  (Bass-wood  or  Bast-wood)  tree.  The 
leather-wood  or  moose-wood  bark,  often  employed  for 
tying  flour-bags,  has  bast-fibers  of  extraordinary  tenacity. 
The  bast  of  the  grape-vine  separates  from  the  stem  in 
long  shreds  a  year  or  two  after  its  formation. 

The  epidermis  of  young  stems  is  replaced,  after  a  cer- 
tain age,  by  the  corky  layer.  This  differs  much  in  dif- 
ferent plants.  In  the  Birch  it  is  formed  of  alternate 
layers  of  large-  and  small-celled  tissue,  and  splits  and 
curls  up.  From  the  Plane-tree  it  is  thrown  off  period- 
ically in  large  plates  by  the  expansion  of  the  cellular  tis- 
sue underneath.  In  the  Maple,  Elm,  and  Oak,  especially 
in  the  Cork-Oak,  it  receives  annual  additions  on  its 
inner  side  and  does  not  separate :  after  a  time  it  conse- 
quently acquires  considerable  thickness,  the  growth  of 
the  stem  furrows  it  with  deep  rifts,  and  it  gradually 
decays  or  drops  away  exteriorly  as  the  newer  bark  forms 
within. 

Pith  Rays. — Those  portions  of  the  first-formed  cell- 
tissue  which  were  interposed  between  the  $oung  and 
originally  an  united  wood- fibers  remain,  and  connect  the 
pith  with  the  cellular  tissue  of  the  bark.  They  inter- 
rupt the  straight  course  of  the  bast- cells,  producing  the 
netted  appearance  often  seen  in  bast  layers,  as  in  the 
Lace-bark.  In  hard  stems  they  become  flattened  by 
the  pressure  of  the  fibers,  and  are  readily  seen  in  most 
kinds  of  wood  when  split  lengthwise.  They  are  espe- 
cially conspicuous  in  the  Oak  and  Maple,  and  form  what 


VEGETATIVE  ORGANS  OF  PLANTS. 


299 


is  commonly  known  as  the  silver-grain.  The  botanist 
terms  them  pith-rays,  or  medullary 
rays. 

Fig.  51  exhibits  a  section  of 
spruce  wood,  magnified  200  di- 
ameters. The  section  is  made 
lengthwise  of  the  wood-cells,  four 
of  which  are  in  part  represented, 
and  cuts  across  the  pith-rays, 
whose  cell-structure  and  position 
in  the  wood  are  seen  at  m,  n. 

Branches  have  the  same  struct- 
ure as  the  stems  from  which  they 
spring.  Their  tissues  traverse 
those  of  the  stem  to  its  center, 
where  they  connect  with  the  pith 
and  its  sheath  of  spiral  ducts. 

Cambium  of  Exogens.  —  The 
growing  part  of  the  exogenous 
stem  is  between  the  fully  formed  wood  and  the  ma- 
ture bark.  There  is,  in  fact,  no  definite  limit  where 
wood  ceases  and  bark  begins,  for  they  are  connected  by 
the  cambial  or  formative  zone,  from  which,  on  the  one 
hand,  wood-fibers,  and  on  the  other,  bast-fibers,  rapidly 
develop.  In  the  cambium,  likewise,  the  pith-rays  which 
connect  the  inner  and  outer  parts  of  the  stem  continue 
their  outward  growth. 

In  spring-time  the  new  cells  that  form  in  the  cambial 
region  are  very  delicate  and  easily  broken.  For  this 
reason  the  rind  or  bark  may  be  stripped  from  the  wood 
without  difficulty.  In  autumn  these  cells  become  thick- 
ened and  indurated — become,  in  fact,  full-grown  bast  and 
wood-cells — so  that  to  peel  the  bark  off  smoothly  is  im- 
possible. 

Minute  Structure  of  Exogenous  Stems. — The  ac- 
companying figure  (52)  will  serve  to  convey  an  idea  of 


51. 


300 


HOW  CROPS  GROW. 


the  minute  structure  of  the  elements  of  the  exogenous 
stem.  It  exhibits  a  section  lengthwise,  through  a  young 
potato  tuber  magnified  200  diameters  ;  a,  b  is  the  rind ; 
e  the  vascular  ring  ;  /  the  pith.  The  outer  cells  of  the 
rind  are  converted  into  cork.  They  have  become  empty 
of  sap  and  are  nearly  impervious  to  air  and  moisture. 
This  corky-layer,  a,  constitutes  the  thin  coat  or  skin  that 
may  be  so  readily  peeled  off  from  a  boiled  potato.  When- 
ever a  potato  is  superficially  wounded,  even  in  winter 
time,  the  exposed  part  heals  over  by  the  formation  of 


cork-cells.  The  cell  tissue  cf  the  rind  consists  at  its 
center,  b,  of  full-formed  cells  with  delicate  membranes 
which  contain  numerous  and  large  starch  grains.  On 
either  hand,  as  the  rind  approaches  the  corky-layer  or 
the  vascular  ring,  the  cells  are  smaller,  and  contain 
smaller  starch  grains  ;  at  either  side  of  these  are  noticed 
cells  containing  no  starch,  but  having  nuclei,  c,  y.  These 
nucleated  cells  are  capable  of  multiplication,  and  they 
are  situated  where  the  growth  of  the  tuber  takes  place. 
The  rind,*  which  makes  a  large  part  of  the  flesh  of  the 
potato,  increases  in  thickness  by  the  formation  of  new 
cells  within  and  without.  Without,  where  it  joins  the 
corky  skin,  the  latter  likewise  grows.  Within,  contigu- 

*The  word  rind  is  here  used  in  its  botanical  (not  in  the  ordinary) 
sense,  to  denote  that  part  of  the  tuber  which  corresponds  to  the  rind  of 
i tie  stem. 


VEGETATIVE  OKGANS  OF  PLANTS. 


301 


ous  to  the  vascular  zone,  new  ducts  are  formed.  In  a 
similar  manner,  the  pith  expands  by 
formation  of  new  cells,  where  it  joins 
the  vascular  tissue.  The  latter  consists, 
in  our  figure,  of  ring,  spiral,  and  dotted 
ducts,  like  those  already  described  as 
occurring  in  the  maize-stalk.  The  deli- 
cate cambial  cells,  c,  are  in  the  region  of 
most  active  growth.  At  this  point  new 
cells  rapidly  develop,  those  to  the  right, 
in  the  figure,  remaining  plain  cells  and 
becoming  loosely  filled  with  starch  ; 
••-•&  those  to  the  left  developing  new  ducts. 

In  the  slender,  overground  potato- 
stem,  as  in  all  the  stems  of  most  agri- 
cultural plants,  the  same  relation  of 
parts  is  to  be  observed,  although  the 
vascular  and  woody  tissues  often  pre- 
ponderate. Wood -cells  are  especially 
abundant  in  those  stems  that  need 
strength  for  the  fulfilment  of  their  offices, 
and  in  them,  especially  in  those  of  our 
trees,  the  structure  is  commonly  more 
complicated. 

Pitted  Wood-Cells  of  the  Coni- 
fers.— In  the  wood  of  cone-bearing  trees 
there  are  no  proper  ducts,  such  as  have 
been  described.  The  large  wood-cells  which  constitute 
the  concentric  rings  of  the  wood  are  constructed  in  a  spe- 
cial manner,  being  provided  laterally  with  pits,  or,  accord- 
ing to  Schacht,  with  visible  pores,  through  which  the 
fluid  contents  of  one  cell  may  easily  diffuse  (by  osmose), 
or  even  pass  directly  into  those  of  its  neighbors. 

Fig.  53,  B  represents  a  portion  of  an  isolated  wood-cell 
of  the  Scotch  Fir  (Pinus  sylvestris)  magnified  200  diam- 
eters. Upon  it  are  seen  nearly  circular  disks,  x,  yt  the 


302 


HOW  CROPS  GROW. 


structure  of  which,  while  the  cell  is  young,  is  shown  by 
a  section  through  them  lengthwise.  A  exhibits  such  a 
section  through  the  thickened  walls  of  two  contiguous 
and  adhering  cells,  x,  in  both  A  and  B,  shows  a  cavity 
between  the  two  primary  cell-walls ;  y  is  the  narrow 
part  of  the  channel,  that 
remains  while  the  mem- 
brane thickens  around  it. 
This  is  seen  at  y,  as  a  pit 
in  each  cell-wall,  or,  as 
Schacht  believed,  a  pore 
or  opening  from  cell  to 
cell.  In  A  it  appears 
closed  because  the  section 
passes  a  little  to  one  side 
^f  the  pore.  (Schacht.) 

In  the  next  figure  (54), 
representing  a  transverse 
section  of  the  spring  wood 
of  the  same  tree  magnified 
300  diameters,  the  struct- 
ure and  the  gradual  form- 
ation of  these  pore-disks 
is  made  evident.  The  sec- 
tion, likewise,  gives  an  in- 
structive  illustration  of 
the  general  character  of  the 
simplest  kind  of  wood.  R 
are  the  young  cells  of  the 
rind  ;  C  is  the  cambium, 
where  cell-multiplication 


Fig.  54. 


goes  on;  W  is  the  wood,  whose  cells  are  more  developed 
the  older  they  are,  i.  e.,  the  more  distant  from  the  cam- 
bium, as  is  seen  from  their  figure  and  the  thickness  of 
their  walls.  At  a  is  shown  the  disk  in  its  earliest  stage  ; 
&  and  c  exhibit  it  in  a  more  advanced  growth.  At  d  the 


VEGETATIVE  OEGAKS  OF  PLANTS.       303 

disk  has  become  a  pore,  the  primary  membrane  has  been 
absorbed,  and  a  free  channel  made  between  the  two  cells. 
The  dotted  lines  at  d  lead  out  laterally  to  two  concentric 
circles,  which  represent  the  disk-pore  seen  flatwise,  as  in 
Fig.  53.  At  e  the  section  passes  through  the  new 
annual  ring  into  the  autumn  wood  of  the  preceding  year. 
Sieve-cells,  or  Sieve-ducts. — The  spiral,  ring,  and 
dotted  ducts  and  pitted  wood-cells  already  noticed,  ap- 
pear only  in  the  older  parts  of  the  vascular  bundles,  and, 
although  they  may  be  occupied  with  sap  at  times  when  the 
stem  is  surcharged  with  water,  they  are  ordinarily  rilled 
with  air  alone.  The  real  transmission  of  the  nutritive 
juices  of  the  growing  plant,  so  far  as  it  goes  on  through 
actual  tubes,  is  now  admitted  to  proceed  in  an  independ- 
ent set  of  ducts,  the  so-called  sieve-tubes,  which  are  usu- 
ally near  to  and  originate  from  the  cambium.  These 
are  extremely  delicate,  elongated  cells,  whose  transverse 
or  lateral  walls  are  perforated,  sieve-fashion  (by  absorp- 
tion of  the  original  membrane)  so  as  to  establish  direct 
communication  from  one  to  another,  and  this  occurs 
while  they  are  yet  charged  with  juices  and  at  a  time 
when  the  other  ducts  are  occupied  with  air  alone.  These 
sieve-ducts  are  believed  to  be  the  channels  through  which 
the  organic  matters  that  are  formed  in  the  foliage  mostly 
pass  in  their  downward  movement  to  nourish  the  stem 
and  root.  Fig.  55  represents  the  sieve-cells  in  the  over- 
ground stem  of  the  potato  ;  A,  B,  cross-section  of  parts 
of  vascular  bundle ;  A,  exterior  part  towards  rind  ;  B, 
interior  portion  next  to  pith ;  a,  a,  cell-tissue  inclosing 
the  smaller  sieve-cells,  A,  B,  which  contain  sap  turbid 
with  minute  granules  ;  b,  cambium  cells  ;  c,  wood-cells 
(which  are  absent  in  the  potato  tuber)  ;  d,  ducts  inter- 
mingled with  wood-cells.  C  represents  a  section  length- 
wise of  the  sieve-ducts  ;  and  D,  more  highly  magnified, 
exhibits  the  finely  perforated,  transverse  partitions, 
through  which  the  liquid  contents  more  or  less  freely 
pass. 


304 


HOW  CEOPS  GROW. 


Milk  Ducts. — Besides  the  ducts  already  described, 
there  is,  in  many  plants,  a  system  of  irregularly  branched 
channels  containing  a  milky  juice  (latex)  as  in  the 
sweet  potato,  dande- 
lion, milk-weed,  etc. 
These  milk-  ducts  a 
occur  in  all  parts  of 
the  plants,  but  most 
abundantly  in  the 
pith  and  inner  bark 
of  stems  and  in  the 
cellular  tissue  of. 


roots.    They  often  so 

completely  permeate 

all  the  organs  of  the 

plant  that  the  slight- 

est   wound    breaks 

some   of    them    and 

causes  a  flow  of  latex. 

The  latter,  like  a 

mal  milk,  is  a  watery 

fluid  holding  in  sus- 

pension minute  gran- 

ules or  drops  which 

make    it    opaque.0 

The  latex  often  con- 

tains the  organic 

substances     peculiar 

to  the  plant,  acquires 

a  sticky,  viscid  char- 

acter,  and   hardens 

on  exposure  to  the  air.     Opium,  India-rubber,  gutta- 

percha,  and  various  resins  are  dried  latex.     Alkaloids 

frequently  occur,  and  ferments  like  papain  (p.  104)  are 

probably  not  uncommon  in  this  secretion. 

Herbaceous  Stems.  —  Annual  steins  of  the  exogenous 


55- 


VEGETATIVE  OBGANS  OF  PLANTS.  305 

kind,  whose  growth  is  entirely  arrested  by  winter,  consist 
usually  of  a  single  ring  of  woody  tissue  with  interiof 
pith  and  surrounding  bark.  Often,  however,  the  zone 
of  wood  is  thin,  and  possesses  but  little  solidity,  while 
the  chief  part  of  the  stem  is  made  up  of  cell-tissue,  so 
that  the  stem  is  herbaceous. 

Woody  Stems. — Perennial  exogenous  stems  consist, 
in  temperate  climates,  of  a  series  of  rings  or  zones,  cor- 
responding in  number  with  that  of  the  years  during 
which  their  growth  has  been  progressing.  The  stems  of 
our  shrubs  and  trees,  especially  after  the  first  few  years  of 
growth,  consist,  for  the  most  part,  of  woody  tissue,  the 
proportion  of  cell-tissue  being  very  small. 

The  annual  cessation  of  growth  which  occurs  at  the 
approach  of  winter  is  marked  by  the  formation  of  smaller 
or  finer  wood-cells,  as  shown  in  Fig.  54,  e,  while  the 
vigorous  renewal  of  activity  in  the  cambium  at  spring- 
time is  exhibited  by  the  growth  of  larger  cells,  and  in 
many  kinds  of  wood  in  the  production  of  ducts,  which, 
as  in  the  oak,  are  visible  to  the  eye  at  the  interior  of  the 
annual  layers. 

Sap-wood  and  Heart-wood. — The  living  processes 
in  perennial  stems,  while  proceeding  with  most  force  in 
the  cambium,  are  not  confined  to  that  locality,  but  go  on 
to  a  considerable  depth  in  the  wood.  Except  at  the 
cambial  layer,  however,  these  processes  consist  not  in  the 
formation  of  new  cells,  nor  the  enlargement  of  those 
once  formed — not  properly  in  growth — but  in  the  trans- 
mission of  sap  and  the  deposition  of  organized  matter  on 
the  interior  of  the  wood-cells.  In  consequence  of  this 
deposition  the  inner  or  heart-wood  of  many  of  our  forest 
trees  becomes  much  denser  in  texture  and  more  durable 
for  industrial  purposes.  It  then  acquires  a  color  differ- 
ent from  the  outer  or  sap-wood  (alburnum),  becomes 
brown  in  most  cases,  though  it  is  yellow  in  the  barberry 
and  red  in  the  red  cedar. 
30 


306  HOW  CEOPS  GROW. 

The  final  result  of  the  filling  up  of  the  cell  of  the 
heart-wood  is  to  make  this  part  of  the  stem  almost  or 
quite  impassahle  to  sap,  so  that  the  interior  wood  may  be 
removed  by  decay  without  disturbing  the  vigor  of  the 
tree. 

Passage  of  Sap  through  the  Stem. — The  stem, 
oesides  supporting  the  foliage,  flowers  and  fruit,  has  also 
a  most  important  office  in  admitting  the  passage  upward 
to  these  organs  of  the  water  and  mineral  matters  which 
enter  the  plant  by  the  roots.  Similarly,  it  allows  the 
downward  transfer  to  the  roots  of  substances  gathered 
by  the  foliage  from  the  atmosphere.  To  this  and  other 
topics  connected  with  the  ascent  and  descent  of  the  sap 
we  shall  hereafter  recur. 

The  stem  constitutes  the  chief  part  by  weight  of  many 
plants,  especially  of  forest  trees,  and  serves  the  most  im- 
portant uses  in  agriculture,  as  well  as  in  a  thousand  other 
industries. 


LEAVES. 

These  most  important  organs  issue  from  the  stem,  are 
at  first  folded  curiously  together  in  the  bud,  and  after- 
wards expand  so  as  to  present  a  great  amount  of  surface 
to  the  air  and  light. 

The  leaf  consists  of  a  thin  membrane  of  cell-tissue 
directly  connected  with  the  cellular  layer  of  the  bark, 
arranged  upon  a  skeleton  or  net-work  of  fibers  and  ducts 
continuous  with  those  of  the  inner  bark  and  wood. 

In  certain  plants,  as  cactuses,  there  scarcely  exist  any 
leaves,  or,  if  any  oecnr,  they  do  fiot  differ,  except  in 
external  form,  from  the  stems.  Many  of  these  pian^ 
above  ground,  are  in  form  all  stem,  while  in  structure 
and  function  they  are  all  leaf. 

In  the  grasses,  although  the  stem  and  leaf  are  distm- 


VEGETATIVE  ORGANS  OF  PLANTS.  307 

guishable  in  shape,  they  are  but  little  unlike  in  other 
external  characters. 

In  forest  trees,  we  find  the  most  obvious  and  striking 
differences  between  the  stem  and  leaves. 

Color  of  Leaves. — A  peculiarity  most  character- 
istic of  the  leaves  of  the  higher  orders  of  plants,  so  long 
as  they  are  in  vigorous  discharge  of  their  proper  vegeta- 
tive activities,  is  the  possession  of  a  green  color,  due  to 
the  presence  of  Chlorophyl.  (See  p.  124.)  This  color 
is  also  proper  in  most  cases  to  the  young  bark  of  the 
stem,  a  fact  further  indicating  the  connection  between 
these  parts,  or  rather  demonstrating  their  identity  of 
origin  and  function,  for  it  is  true,  not  only  in  the  case 
of  the  cactuses,  but  also  in  that  of  all  other  young 
plants,  that  the  green  (young)  stems  perform,  to  some 
extent,  the  same  offices  as  the  leaves,  the  latter  being,  in 
fact,  growths  from  and  extensions  of  the  bark. 

The  loss  of  green  color  that  occurs  in  autumn,  in  the 
foliage  of  our  deciduous  trees,  or  on  the  maturing  of  the 
plant,  as  with  the  cereal  grains,  is  related  to  the  cessa- 
tion of  growth  and  death  of  the  leaf,  and  results  from 
chemical  changes  in  the  chlorophyl-pigment. 

Plants  naturally  destitute  of  chlorophyl,  like  Indian 
pipe  (Monotropa),  Dodder  (Cuscuta),  Mushrooms, 
Toadstools,  and  fungi  generally,  are  parasites  on  living 
or  dead  organisms,  from  which  they  derive  their  nour- 
ishment. Such  plants  cannot  construct  organic  sub- 
stances out  of  inorganic  matters,  as  do  the  plants  having 
chlorophyl. 

When  leaves,  ordinarily  green,  are  totally  excluded 
from  light,  or  develop  at  a  low  temperature,  they  have  a 
pale  yellow  color ;  on  exposure  to  light  and  warmth  they 
become  green.  In  both  cases  the  C hlorophyl-granules 
are  formed,  but  the  chlorophyl-pigment  appears  onlv  in 
the  latter.  In  absence  of  iron,  leaves  are  white, 
no  chlorophyl  granules,,  and  growth  is  arrested. 


308  HOW  CROPS  GROW. 

There  are  many  leafy  plants  cultivated  for  ornamental  purposes 
with  more  or  less  brown,  red,  yellow,  white,  or  variegated  foliage, 
which  are  by  no  means  destitute  of  chlorophyl,  as  is  shown  by  micro- 
scopic examination,  though  this  substance  is  associated  with  other 
coloring  matters  which  mask  its  green  tint. 

Structure  of  Leaves. — While  in  shape,  size,  modes 
of  arrangement  upon  and  attachment  to  the  stem,  we 
find  among  leaves  no  end  of  diversity,  there  is  great  sim- 
plicity in  the  matter  of  their  internal  structure. 

The  whole  surface  of  the  leaf,  on  both  sides,  is  cov- 
ered with  epidermis,  &  coating  which,  in  many  cases, 
may  be  readily  stripped  off  the  leaf,  and  consists  of  thick- 
walled  cells,  which  are,  for  the  most  part,  devoid  of  liq- 
uid contents,  except  when  very  young.  (E,  E,  Fig.  56.) 

Fig.  56  represents  the  appearance  of  a  bit  of  bean-leaf  as  seen  on  a 
section  from  the  upper  to  the  lower  surface,  and  highly  magnified. 

Below  the  upper  epidermis,  there  often  occur  one  or 
more  layers  of  oblong  cells,  whose  sides  are  in  close  con- 
tact, and  which  are  arranged  endwise,  with  reference  to 
the  flat  of  the  leaf.  Below  these,  down  to  the  lower  epi- 
dermis, for  one-half  to  three-quarters  of  the  thickness  of 
the  leaf,  the  cells  are  commonly  spherical  or  irregular  in 
figure  and  arrangement,  and  more  loosely  disposed,  with 
numerous  and  large  interspaces. 

The  interspaces  among  the  leaf-cells  are  occupied  with 
air,  which  is  also,  in  most  cases,  the 
only  content  of  the  epidermal  cells. 
The  interior  cells  of  the  leaf  are  filled 
with  sap  and  contain  the  chlorophyl- 
granules.  Under  the  microscope,  these 
are  commonly  seen  attached  to  the  walls 
of  the  cells,  as  in  Fig.  56,  or  coating 
grains  of  starch,  or  else  floating  free  in 
the  cell-sap. 

The  structure  of  the  veins  or  ribs  of 
the  leaf  is  similar  to  that  of  the  vascular 
Fig.  56         bundles  of  the  stem,  of  which  they  are 
branches.     At  a,  Fig.  56,  is  seen  the  cross  section  of  a 
vein  in  the  bean-leaf. 


VEGETATIVE  ORGANS  OF  PLANTS.  309 

The  epidermis,  while  often  smooth,  is  frequently  beset 
with  hairs  or  glands,  as  seen  in  the  figure.  These  are 
variously  shaped  cells,  sometimes  empty,  sometimes,  as 
in  the  nettle,  filled  with  an  irritating  liquid. 

Leaf-Pores. — The  epidermis  of  the  mature  leaf  is  pro- 
vided with  a  vast  number  of  "breathing  pores,"  or  stomata, 
by  means  of  which  the  intercellular  spaces  in  the  interior 
of  the  leaf  are  brought  into  direct  communication  with 
the  outer  atmosphere.  Each  of  these  stomata  consists 
usually  of  two  curved  guard-cells,  which  are  disposed 

toward  each  other  like  the 
halves  of  an  elliptical  car- 
riage-spring. (Figs.  52  and 
53.)  The  opening  between 
them  is  an  actual  orifice  in 
the  skin  of  the  leaf.  The 
size  of  the  orifice  is,  how- 
ever, constantly  changing, 
as  the  atmosphere  becomes 
drier  or  more  moist,  and  as 
the  sunlight  acts  more  or 

less  intensely  on  its  surface.  In  strong  light  they  curve 
outwards,  and  the  aperture  is  enlarged  ;  in  darkness  they 
straighten  and  shut  together,  like  the  springs  of  a  heavily- 
loaded  carriage,  and  nearly  or  entirely  close  the  entrance. 
The  effect  of  water  usually  is  to 
3lose  their  orifices. 

In  Fig.  56  is  represented  a  section^ 
through  the  shorter  diameter  of  a  pore 
on  the  under  surface  of  a  bean-leaf. 
The  air-space  within  it  is  shaded  black. 
Unlike  the  other  epidermal  cells,  those 
of  the  leaf-pores  contain  chlorophyll 
granules. 

Fig.  57  represents  a  portion  of  the  epi- 
dermis of  the  upper  surface  of  a  potato- 
leaf,  and  Fig.  58  a  similar  portion  of  the  Fig.  58. 
under  surface  of  the  same  leaf,  magnified 

200  diameters.    In  both  figures  are  seen  the  open  stomata  between  the 
semi-elliptical  cells.    The  outlines  of  the  other  epidermal  cells  ar« 


310  HOW  CHOPS  GROW. 

marked  by  irregular  double  lines.  The  round  bodies  in  the  guard- 
cells  of  the  pores  are  starch-grains,  often  present  in  these  cells,  when 
not  existing  in  any  other  part  of  the  leaf. 

The  stomata  are,  with  few  exceptions,  altogether  want- 
ing on  the  submerged  leaves  of  aquatic  plants.  On 
floating  leaves  they  occur,  but  only  on  the  upper  surface. 
Thus,  as  a  rule,  they  are  not  found  in  contact  with 
liquid  water.  On  the  other  hand,  they  are  either  absent 
from,  or  comparatively  few  in  number  upon,  the  upper 
surfaces  of  the  foliage  of  land  plants,  which  are  exposed 
to  the  heat  of  the  sun,  while  they  occur  abundantly  on 
the  lower  sides  of  all  green  leaves.  In  number  and  size 
they  vary  remarkably.  Some  leaves  possess  but  800  to 
the  square  inch,  while  others  have  as  many  as  170,000  to 
that  amount  of  surface.  About  100,000  may  be  counted 
on  an  average-sized  apple-leaf.  In  general,  they  are 
largest  and  most  numerous  on  plants  which  belong  to 
damp  and  shaded  situations,  and  then  exist  on  both  sides 
of  the  leaf. 

The  epidermis  itself  is  most  dense — consists  of  thick- 
walled  cells  and  several  layers  of  them — in  case  of  leaves 
which  belong  to  the  vegetation  of  sandy  soils  in  hot  cli- 
mates. Often  it  is  impregnated  with  wax  on  its  upper 
surface,  and  is  thereby  made  almost  impenetrable  to 
moisture.  On  the  other  hand,  in  rapidly-growing  plants 
adapted  to  moist  situations,  the  epidermis  is  thin  and 
delicate. 

Exhalation  of  Water-Vapor. — A  considerable  loss 
of  water  goes  on  from  the  leaves  of  growing  plants  when 
they  are  freely  exposed  to  the  atmosphere.  The  water 
thus  lost  exhales  in  the  form  of  invisible  vapor.  The 
quantity  of  water  exhaled  from  any  plant  may  be  easily 
ascertained,  provided  it  is  growing  in  a  pot  of  glazed 
earthen  or  other  impervious  material.  A  metal  or  glass 
cover  is  cemented  air-tight  to  the  rim  of  the  vessel,  and 
around  the  stem  of  the  plant.  The  cover  has  an  open- 


VEGETATIVE  OBGANS  OF  PLANTS.  311 

ing  with  a  cork,  through  which  weighed  quantities  of 
water  are  added  from  time  to  time,  as  required.  The 
amount  of  exhalation  during  any  given  interval  of  time 
is  learned  with  a  close  approach  to  accuracy  by  simply 
noting  the  loss  of  weight  which  the  plant  and  pot 
together  suffer.  Hales,  who  first  experimented  in  this 
manner,  found  that  a  vigorous  sunflower,  three  and  a 
half  feet  high,  whose  foliage  had  an  aggregate  surface  of 
39  square  feet,  gave  off  30  ounces  av.  of  water  in  a  space 
of  12  hours,  during  a  very  warm,  dry  day.  The  average 
"rate  of  perspiration"  for  15  days,  in  July  and  August, 
was  20  ounces  av.  At  night,  with  "any  sensible,  though 
small  dew,  the  perspiration  was  nothing."  Knop 
observed  a  maize-plant  to  exhale,  between  May  22d  and 
September  4th,  no  less  than  36  times  its  weight  of  water. 
Hellriegel  (at  Dahme,  Prussia)  found  that  summer 
wheat  and  rye,  oats,  beans,  peas,  buckwheat,  red  clover, 
yellow  lupine  and  summer  colza,  on  the  average  exhaled 
300  grams  of  water  for  1  gram  of  dry  matter  produced 
above  ground,  during  the  entire  season  of  growth,  when 
stationed  in  a  sandy  soil.  (Die  Methode  der  Sandkultur, 
p.  662.) 

Exhalation  is  not  a  regular  or  uniform  process,  but 
varies  with  a  number  of  circumstances  and  conditions. 
It  depends  largely  upon  the  dryness  and  temperature  of 
the  air.  When  the  air  is  in  the  state  most  favorable  to 
evaporation,  the  loss  from  the  plant  is  rapid  and  large. 
When  the  air  is  loaded  with  moisture,  as  during  dewy 
nights  or  rainy  weather,  then  exhalation  is  nearly  or 
totally  checked. 

The  temperature  of  the  soil,  and  even  its  chemical 
composition,  the  condition  of  the  leaf  as  to  its  texture, 
age,  and  number  of  stomata,  likewise  affect  the  rate  of 
exhalation. 

Exhalation  is  rather  incidental  than  necessary  to  the 
life  of  many  plants,  since  it  may  be  suppressed  or  reduced 


312 


HOW  CEOPS  GROW. 


to  a  minimum,  as  in  a  Wardian  case  or  fernery,  without 
evident  influence  on  growth  ;  but  plants  of  parentage 
naturally  accustomed  to  copious  exhalation  of  water 
flourish  best  where  the  conditions  are  favorable  to  this 
process.  Exhalation  is  not  injurious,  unless  the  loss 
be  greater  than  the  supply.  If  water  escapes  from  the 
leaves  faster  than  it  enters  the  roots,  the  succulent  organs 
soon  wilt,  and  if  this  disturbance 
goes  on  too  far  the  plant  dies. 

Exhalation  ordinarily  proceeds  to 
a  large  extent  from  the  surface  of 
the  epidermal  cells.  Although  the 
cavities  of  these  cells  are  chiefly  oc- 
cupied with  air,  their  thickened  walls 
transmit  outward  the  water  which  is 
supplied  to  the  interior  of  the  leaf. 
Otherwise  the  escape  of  vapor  occurs 
through  the  stomata.  These  pores 
appear  to  have  the  function  of  facil- 
itating exhalation,  by  their  property 
of  opening  when  exposed  to  sunlight. 
Thus  evaporation  from  the  leaves  is 
favored  at  the  time  when  root-action 
is  most  vigorous,  and  the  plant  is  to 
the  greatest  degree  surcharged  with 
water. 

Access  of  Air  to  the  Interior 
of  the   Plant. — Not  only  does  the 
leaf  allow  the  escape  of  vapor  of  water,  but  it  admits  of 
the  entrance  and  exit  of  gaseous  bodies. 

The  particles  of  atmospheric  air  have  easy  access  to 
the  interior  of  all  leaves,  however  dense  and  close  their 
epidermis  may  be,  however  few  or  small  their  stomata. 
All  leaves  are  actively  engaged  in  absorbing  or  exhaling 
certain  gaseous  ingredients  of  the  atmosphere  during 
the  whole  of  their  healthy  existence. 


Fig.  59. 


EEPEODUCTIVE  OEGANS  OF  PLANTS.  313 

The  entire  plant  is,  often,  pervious  to  air  through 
the  stomata  of  the  leaves.  These  communicate  with  the 
intercellular  spaces  of  the  leaf,  which  are,  in  general, 
occupied  exclusively  with  air,  and  these  again  connect 
with  the  ducts  which  ramify  throughout  the  veins  of  the 
leaf  and  branch  from  the  vascular  bundles  of  the  stem. 
In  the  bark  or  epidermis  of  woody  stems,  as  Hales  long 
ago  discovered,  pores  or  cracks  exist,  through  which 
the  air  has  communication  with  the  longitudinal  ducts. 

These  facts  admit  of  demonstration  by  simple  means.  Sachs  employs 
for  this  purpose  an  apparatus  consisting  of  a  short,  wide  tube  of  glass, 
£,  Fig.  59,  to  which  is  adapted,  below,  by  a  tightly-fitting  cork,  a  bent 
glass  tube.  The  stem  of  a  leaf  is  passed  through  a  cork  which  is  then 
secured  air-tight  in  the  other  opening  of  the  wide  tube,  the  leaf  itself 
being  included  in  the  latter,  and  the  joints  are  made  air-tight  by  smear- 
ing with  tallow.  The  whole  is  then  placed  in  a  glass  jar  containing 
enough  water  to  cover  the  projecting  leaf -stem,  and  merctiry  is  quickly 
poured  into  the  open  end  of  the  bent  tube,  so  as  nearly  to  fill  the  lat« 
ter.  The  pressure  of  the  column  of  this  dense  liquid  immediately 
forces  air  into  the  stomata  of  the  leaf,  and  a  corresponding  quantity  is 
forced  on  through  the  intercellular  spaces  and  through  the  vein  ducts 
into  the  ducts  of  the  leaf-stem,  whence  it  issues  in  fine  bubbles  at  S. 
It  is  even  easy  in  many  cases  to  demonstrate  the  permeability  of  the 
leaf  to  air  by  immersing  it  in  water,  and,  taking  the  leaf -stem  between 
the  lips,  produce  a  current  by  blowing.  In  this  case  the  air  escapes 
from  the  stomata. 

The  air-passages  of  the  stem  may  be  shown  by  a  similar  arrange- 
ment, or  in  many  instances,  as,  for  example,  with  a  stalk  of  maize,  by 
simply  immersing  one  end  in  water  and  blowing  into  the  other. 

On  the  contrary,  roots  are  destitute  of  any  visible 
external  pores,  and  are  not  pervious  to  air  or  vapor  in 
the  sense  that  leaves  and  young  stems  are. 

The  air  passages  in  the  plant  correspond  roughly  to 
the  mouth,  throat,  and  breathing  cavities  of  the  animal. 
We  have,  as  yet,  merely  noticed  the  direct  communica- 
tion of  these  passages  with  the  external  air  by  means  of 
microscopically  visible  openings.  But  the  cells  which 
are  not  visibly  porous  readily  allow  the  access  and  egress 
of  water  and  of  gases  by  osmose.  To  the  mode  in  which 
this  is  effected  we  shall  recur  on  subsequent  pages. 

The  Offices  of  Foliage  are  to  put  the  plant  in  com- 
munication with  the  atmosphere  and  with  the  sun.  On 


314  HOW  CROPS  GROW. 

the  one  hand  it  permits,  and  to  a  certain  degree  facili- 
tates, the  escape  of  the  water  which  is  continually 
pumped  into  the  plant  by  its  roots,  and  on  the  other 
hand  it  absorbs,  from  the  air  that  freely  penetrates  it, 
certain  gases  which  furnish  the  principal  materials  for 
the  construction  of  vegetable  matter.  We  have  seen  that 
the  plant  consists  of  elements,  some  of  which  are  volatile 
at  the  heat  of  ordinary  fires,  while  others  are  fixed  at 
this  temperature.  When  a  plant  is  burned,  the  former, 
to  the  extent  of  90  to  99  per  cent  of  the  plant,  are  con- 
verted into  gases,  the  latter  remain  as  ashes. 

The  reorganization  of  vegetation  from  the  products  of 
its  combustion  (or  decay)  is,  in  its  simplest  phase,  the 
gathering  by  a  new  plant  of  the  ashes  from  the  soil 
through  its  roots,  and  of  these  gases  from  the  air  by  its 
leaves,  and  the  compounding  of  these  comparatively  sim- 
ple substances  into  the  highly  complex  ingredients  of  the 
vegetable  organism.  Of  this  work  the  leaves  have  by 
far  the  larger  share  to  perform;  hence  the  extent  of 
their  surface  and  their  indispensability  to  the  welfare  of 
the  plant. 


CHAPTEK  IV. 
REPRODUCTIVE  ORGANS  OF  PLANTS. 

§1- 
MODES   OF   REPRODUCTION. 

Plants  are  reproduced  in  various  ways.  The  simplest 
cellular  plants  have  no  evident  special  organs  of  repro- 
duction, but  propagate  themselves  solely  by  a  process  of 
division  which  begins  in  the  protoplasm,  as  already  de- 
scribed in  case  of  Yeast,  p.  253.  The  lower  so-called 
flowerless  plants  (Cryptogams),  including  molds,  blights, 
mildews,  mushrooms,  toadstools  (Fungi),  mosses,  lichens, 


REPRODUCTIVE  ORGANS  OF  PLANTS.  315 

etc.,  reproduce  themselves  in  part  by  spores,  each  of 
which  is  a  single  minute  cell  that  is  capable  of  develop- 
ing into  a  plant  like  that  from  which  ib  was  thrown  off. 

In  very  many  cases  a  portion  or  " cutting"  of  root, 
stem  or  leaf,  from  herb  or  tree,  placed  in  moist,  warm 
earth,  will  grow  and  develop  into  a  new  plant  in  all 
respects  similar  to  the  original.  The  potato,  grape, 
banana,  and  sugar-cane  plants  are  almost  exclusively 
propagated  in  this  manner.  In  budding  and  grafting  a 
portion  of  stem,  carrying  a  single  bud  or  a  number  of 
buds  (scion),  is  planted,  not  in  the  soil,  but  in  the  cam- 
bial  layer  of  a  living  root  or  stem  with  which  it  unites 
and  thenceforward  grows. 

The  higher  orders  of  plants  (Phanerogams)  have  spe- 
cial reproductive  organs,  constituting  or  contained  in 
their  flowers,  whose  office  it  is  to  produce  seed,  the  essen- 
tial part  of  which  is  the  embryo,  a  ready-formed  minia- 
ture plant  which  may  grow  into  the  full  likeness  of  its 
parent. 

§o 
a, 

THE   FLOWER. 

In  the  higher  plants  the  onward  growth  of  the  stem  or 
of  its  branches  is  not  necessarily  limited,  until  from  the 
terminal  buds,  instead  of  leaves,  only  flowers  unfold. 
When  this  happens,  as  is  the  case  with  most  annual  and 
biennial  plants,  raised  on  the  farm  or  in  the  garden,  the 
vegetative  energy  has  usually  attained  its  fullest  develop- 
ment, and  the  reproductive  function  begins  to  prepare 
for  the  death  of  the  individual  by  providing  seeds  which 
shall  perpetuate  the  species. 

There  is  often  at  nrst  no  apparent  difference  between 
the  leaf-buds  and  flower-buds,  but  commonly,  in  the  later 
stages  of  their  growth,  the  latter  are  to  be  readily  dis- 
tinguished from  the  former  by  their  greater  size,  and  by 
peculiar  shape  or  color. 


316 


HOW  CROPS  GROW. 


The  Flower  is  a  short  branch,  bearing  a  collection  of 
organs,  which,  though  usually  having  little  resemblance 
to  foliage,  may  be  considered  as  leaves,  more  or  less  mod- 
ified in  form,  color,  and  office. 

The  flower  commonly  presents  four  different  sets  of 
organs,  viz.,  Calyx,  Corolla,  Stamens,  and  Pistils,  and  is 
then  said  to  be  complete,  as  in  case  of  the  apple,  potato, 
and  many  common  plants.  Fig.  60  represents  the  com- 
plete flower  of  the  Fuchsia,  or  ladies'  ear-drop,  now  uni- 
versally cultivated.  In  Fig.  61  the  same  is  shown  in 
section. 

The  Calyx  (cup)  ex,  is  the  outermost  floral  envelope. 
Its  color  is  red  or  white  in  the  Fuchsia,  though  generally 
it  is  green.  When  it  consists  of  several  distinct  leaves, 

they  are   called 

sepals.    The  calyx 

is  frequently  small 

and     inconspicu- 
ous.     In     some 

cases  it  falls  away 

as     the     flower 

opens.     In  the 

Fuchsia  it  firmly 

adheres  at  its  base 

i  to  the  seed-vessel, 

vand  is  divided  into 

1  four  lobes. 

The     Corolla 

(crown),  c,  or  ca, 

is   one   or   several 

series  of   leaves 

which  are  situated 
within  the  calyx.  It  is  usually  of  some  other  than  a 
green  color  (in  the  Fuchsia,  purple,  etc.),  often  has 
marked  peculiarities  of  form  and  great  delicacy  of  struc- 
ture, and  thus  chiefly  gives  beauty  to  the  flower.  When 


•st 


Fig.  60. 


Fig.  61. 


REPRODUCTIVE  ORGANS  OF  PLANTS.  317 

the  corolla  is  divided  into  separate  leaves,  these  are 
termed  petals.  The  Fuchsia  has  four  petals,  which  are 
attached  to  the  calyx-tube. 

The  Stamens,  s,  in  Figs.  60  and  61,  are  generally 
slender,  thread-like  organs,  terminated  by  an  oblong 
sack,  the  anther,  which,  when  the  flower  attains  its  full 
growth,  discharges  a  fine  yellow  or  brown  dust,  the  so- 
called  pollen. 

The  anthers,  as  well  as  the  grains  of  pollen,  vary  in  form  with  nearly 
every  kind  of  plant.  The  yellow  pollen  of  Pine  and  Spruce  is  not  in- 
frequently  transported  by  the  wind  to  a  great  distance,  and  when 
brought  down  by  rain  in  considerable  quantities,  has  been  mistaken 
for  sulphur. 

The  Pistil,  p,  in  Figs.  60  and  61,  or  pistils,  occupy 
the  center  of  the  perfect  flower.  They  are  exceedingly 
various  in  form,  but  always  have  at  their  base  the  seed- 
vessels,  or  ovaries,  ov,  in  which  are  found  the  ovules  or 
rudimentary  seeds.  The  summit  of  the  pistil  is  desti- 
tute of  the  epidermis  which  covers  all  other  parts  of  the 
plant,  and  is  termed  the  stigma,  st. 

As  has  been  remarked,  the  floral  organs  may  be  consid- 
ered to  bo  modified  leaves  ;  or  rather,  all  the  appendages 
of  the  stem — the  leaves  and  the  parts  of  the  flower  to- 
gether— are  different  developments  of  one  fundamental 
structure. 

The  justness  of  this  idea  is  sustained  by  the  transform- 
ations which  are  often  observed. 

The  Rose  in  its  natural  state  has  a  corolla  consisting 
of  five  petals,  but  has  a  multitude  of  stamens  and  pistils. 
In  a  rich  soil,  or  as  the  effect  of  those  agencies  which  are 
united  in  "cultivation,"  nearly  all  the  stamens  lose  their 
reproductive  function  and  proper  structure,  and  revert 
to  petals ;  the  flower  becoming  "double."  The  tulip, 
poppy,  and  numerous  garden-flowers,  illustrate  this  in- 
teresting metamorphosis,  and  in  these  flowers  we  may 
often  see  the  various  stages  intermediate  between  the 
perfect  petal  and  the  unaltered  stamen. 


318  HOW   CROPS   GROW. 

On  the  other  hand,  the  reversion  of  all  the  floral 
organs  into  ordinary  green  leaves  has  been  observed  not 
infrequently,  in  case  of  the  rose,  white  clover,  and  other 
plants. 

While  the  complete  flower  consists  of  the  four  sets  of 
organs  above  described,  only  the  stamens  and  pistils  are 
essential  to  the  production  of  seed.  The  latter,  accord- 
ingly, constitute  a  perfect  flower,  even  in  the  absence  of 
calyx  and  corolla. 

The  flower  of  buckwheat  has  no  corolla,  but  a  white  or 
pinkish  calyx. 

The  grasses  have  flowers  in  which  calyx  and  corolla  are 
represented  by  scale-like  leaves,  which,  as  the  plants  ma- 
ture, become  chaff. 

In  various  plants  the  stamens  and  pistils  are  borne  on 
separate  flowers.  Such  are  called  moncecious  plants,  of 
which  the  birch  and  oak,  maize,  melon,  squash,  cucum- 
ber, and  often  the  strawberry,  are  examples. 

In  case  of  maize,  the  staminate  flowers  are  the  "tas- 
sels "  at  the  summit  of  the  stalk ;  the  pistillate  flowers 
are  the  young  ears,  the  pistils  themselves  being  the 
"  silk,"  each  fiber  of  which  has  an  ovary  at  its  base,  that, 
if  fertilized,  develops  to  a  kernel. 

Dioecious  plants  are  those  which  bear  the  staminate 
(male,  or  sterile)  flowers  and  the  pistillate  (female,  or 
fertile)  flowers  on  different  individuals ;  the  willow,  the 
hop- vine,  and  hemp,  are  of  this  kind. 

Nectaries  are  special  organs — glands  or  tubes — secret- 
ing a  sugary  juice  or  nectar,  which  serves  as  food  to 
insects.  The  clovers  and  honeysuckles  furnish  familiar 
examples. 

Fertilization  and  Fructification — The  grand  func- 
tion of  the  flower  is  fructification.  For  this  purpose 
pollen  must  fall  upon  or  be  carried  by  wind,  insects,  or 
other  agencies,  to  the  naked  tip  of  the  pistil.  Thus  sit- 
uated, each  pollen-grain  sends  out  a  slender  microscopic 


REPRODUCTIVE   ORGANS  OF  PLANTS.  319 

tube  which  penetrates  the  interior  of  the  pistil  until  it 
enters  the  seed-vessel  and  conies  in  contact  with  the  ovule 
or  rudimentary  seed.  This  contact  being  established, 
the  ovule  is  fertilized  and  begins  to  grow.  Thencefor- 
ward the  corolla  and  stamens  usually  wither,  while  the 
base  of  the  pistil  and  the  included  ovules  rapidly  increase 
in  size  until  the  seeds  are  ripe,  when  the  seed-vessel  falls 
to  the  ground  or  else  opens  and  releases  its  contents. 

Fig.  62  exhibits  the  process  of  fertilization  as  observed 
in  a  plant  allied  to  buckwheat,  viz.,  the  Polygonum  con- 
volvulus. The  cut  represents  a  magnified  section  length- 
wise through  the  short  pistil ;  a  is  the  stigma  or  summit 
of  the  pistil ;  5  are  grains  of  pollen ; 
c  are  pollen  tubes  that  have  penetrated 
into  the  seed-vessel  which  forms  the 
base  of  the  pistil ;  one  has  entered  the 
mouth  of  the  rudimentary  seed,  g,  and 
reached  the  embryo  sack,  e,  within 
which  it  causes  the  development  of  a 
germ ;  d  represents  the  interior  wall 
of  the  seed-vessel ;  h,  the  base  of  the 
seed  and  its  attachment  to  the  seed- 
vessel. 

Self-Fertilization  occurs  when 
ovules  are  impregnated  by  pollen 
from  the  same  flower.  In  many  plants 
self-fertilization  is  favored  by  the  posi- 
tion of  the  organs  concerned.  In  the 
pendent  flower  of  the  Fuchsia  as  well  Fi£-  62- 

as  in  the  upright  one  of  the  strawberry  the  stigma  is  just 
below  and  surrounded  by  the  anthers,  so  that  when  the 
mature  pollen  is  discharged  it  cannot  fail  to  fall  upon  the 
stigma.  Some  flowers,  as  those  of  the  closed  gentian 
(Oentiana  Andreiusii)  and  the  small  subterranean  blos- 
soms of  sheep-sorrel  (Oxalis  acetosella),  touch-me-not 
(Impatiens),  and  of  many  violets,  never  open,  and  not 


320  HOW  CROPS  GEOW. 

only  are  self-fertile  but  cannot  well  be  otherwise.  Some 
plants  which,  carry  these  closed  and  inconspicuous  subter- 
ranean flowers  depend  upon  them  for  reproduction  by 
seed,  their  large  and  showy  serial  flowers  being  often  bar- 
ren, as  in  violets,  or  totally  infertile  ( Voandzeia. )  Flax 
and  turnips  are  self-fertilizing. 

Cross-Fertilization  results  from  the  contact  of  the 
pollen  of  one  flower  with  the  ovules  of  another.  In  many 
plants  remarkable  arrangements  exist  that  hinder  or 
totally  prevent  self-fertilization  and  favor  or  ensure  cross- 
fertilization. 

In  monoecious  plants,  as  hazel  or  squash,  flowers  of  one 
sort  yield  pollen,  others,  different,  contain  the  ovules ; 
so  that  two  distinct  and  more  or  less  distant  blossoms  of 
the  same  plant  are  necessary  for  seed-production. 

In  the  dioecious  poplar  and  hops,  the  plant  that  pro- 
duces pollen  never  carries  ovules  and  that  which  bears  the 
latter  is  destitute  of  the  former,  so  that  two  distinct 
plants  must  co-operate  to  form  seeds. 

It  often  happens  that  the  pollen  of  a  flower  cannot  fer- 
tilize the  ovules  of  the  same  flower.  This  may  be  either 
because  the  stigma  is  behind  the  pollen  in  development, 
as  in  case  of  various  species  of  geranium,  or  because  the 
stigma  has  passed  its  receptive  period  before  the  pollen  is 
mature,  as  in  Sweet  Vernal  Grass  (Antlioxanthum  odo- 
ratum).  In  both  instances  the  ripened  pollen  may  reach 
stigmas  that  are  ready  in  other  flowers  and  fertilize  their 
ovules,  insects  being  often  the  means  of  transportation. 

In  a  large  number  of  flowers,  whose  pollen  and  stigmas 
are  simultaneously  prepared,  the  position  of  the  organs 
is  such  that  self-fertilization  is  difficult  or  impossible. 
The  Iris,  Crocus,  Pansy,  Milk-weed  (Asdepias),  and  many 
Orchids,  are  of  this  class.  The  offices  of  insects  in  search 
of  nectar,  or  attracted  by  odors,  are  here  indispensable. 
The  common  red  clover  cannot  produce  seed  without 
insect  aid,  and  the  bumblebee  customarily  performs  this 


REPRODUCTIVE  OitGANS  OF  PLANTS.  321 

service.  The  insect,  in  exploring  a  flower  for  nectar, 
leaves  upon  its  stigma  pollen  taken  from  the  flower  last 
visited,  and  in  emerging  renews  its  burden  of  pollen  to 
bestow  it  in  turn  upon  the  stigma  of  a  third  flower. 

Cross-fertilization  is  doubtless  often  effected  by  insects 
in  case  of  flowers  which  are  in  all  respects  adapted  for 
self-fertilization,  while  flowers  that  casual  examination 
would  pronounce  self-fertile  are  in  fact  of  themselves 
sterile.  The  flowers  of  rye  open  singly,  the  long  stamens 
shortly  mature  and  discharge  their  pollen,  which  falls  on 
the  stigmas  of  flowers  standing  lower  in  the  same  head, 
or  on  neighboring  heads.  According  to  Kimepare,  the 
individual  rye-flower  can  fertilize  neither  itself  nor  the 
different  flowers  of  an  ear,  nor  can  the  different  ears  of 
one  and  the  same  plant  pollinate  one  another  with  suc- 
cess, although  no  mechanical  hindrance  exists.  (Sachs, 
Physiology  of  Plants,  p.  790.) 

Results  of  Self-Fertilization  and  Cross-Fertili- 
zation.— Spreugel,  one  of  the  early  students  of  Plant- 
Reproduction,  wrote  in  1793,  "  Nature  appears  to  be 
unwilling  that  any  flower  shall  be  fertilized  by  its  own 
pollen."  Extensive  observation  indicates  decidedly 
that  cross-fertilization  is  far  more  general  than  self- 
fertilization,  especially  among  the  higher  plants.  Dar- 
win has  shown  that,  in  many  cases,  the  pollen  of  a  flower 
is  incapable  of  fertilizing  its  own  ovules,  and  that  the 
pollen  from  another  flower  of  the  same  plant  is  scarcely 
more  potent.  In  these  cases  the  pollen  from  a  -flower 
borne  by  another  plant  of  the  same  kind  is  potent,  and 
the  more  so  the  more  unlike  the  two  plants  are. 

In  Darwin's  trials  on  the  reproduction  of  the  Morning 
Glory,  Ipomea  purpurea,  carried  out  through  ten  gener- 
ations, the  average  height  of  73  self-fertilized  plants  was 
66  inches,  while  that  of  the  same  number  of  crossed 
plants  was  85.8  inches,  or  in  the  ratio  of  77  to  100. 
The  relative  number  of  seeds  produced  by  the  self-fertil' 
31 


322  SOW  CHOPS  GKOW. 

ized  and  cross-fertilized  plants  in  the  1st,  3d,  and  9tli 
generations  were  respectively  as  64  to  100;  35  to  100, 
and  26  to  100. 

In  other  cases,  but,  so  far  as  observed,  much  less  com- 
monly, self-fertilization  gives  the  best  results  both  as 
regards  numbers  and  vigor  of  offspring.  In  Darwin's  ex- 
periments a  variety  of  Mimulus  luteus  originated,  of 
which  the  self-fertilized  progeny  surpassed  the  cross-fer- 
tilized, during  several  generations.  In  the  seventh  gen- 
eration the  ratio  of  superiority  of  the  self -fertilized,  as 
regards  numbers  of  fruit,  was  as  137  to  100,  and  in  respect 
to  size  of  plants  as  126  to  100. 

Continued  self-fertilization,  is  thus  limited  by  its  ten- 
dency, as  statistically  determined,  to  reduce  both  the 
vegetative  and  reproductive  vigor  of  the  plant.  On  the 
other  hand,  cross-fertilization  is  possible  or  practicable 
only  within  very  narrow  bounds,  and  the  increased  pro- 
ductiveness that  follows  it  soon  reaches  a  limit,  as  is 
shown  by  the  history  of  vegetable  hybrids. 

That  neither  mode  of  fertilization  is  exclusively  or  speci- 
ally adapted  to  the  highest  development  of  plants  in  gen- 
eral, or  of  particular  kinds  of  plants,  is  shown  by  the  fact 
that  in  the  course  of  Darwin's  researches  on  the  Ipomea 
purpurea,  just  referred  to,  in  the  sixth  generation  a  self- 
fertilized  plant  (variety)  appeared,  which  was  superior  to 
its  crossed  collateral,  and  was  able  to  transmit  its  vigor 
and  fertility  to  its  descendants. 

It  is  evident,  therefore,  that  the  causes  which  lead  to 
higher  development  co-operate  most  fully,  sometimes  in 
the  one,  sometimes  in  the  other,  mode  of  impregnation 
and  do  not  necessarily  belong  to  either.  We  must  be- 
lieve that  excellence  in  offspring  is  the  result  of  excel- 
lence in  the  parents,  no  matter  what  lines  their  heredity 
may  have  followed,  except  as  these  lines  have  influenced 
their  individual  excellence.  That  crossing  commonly 
gives  better  offspring  than  in-and-in  breeding  is  due  to 


REPRODUCTIVE  ORGANS  OF  PLANTS.  323 

the  fact  that  in  the  latter  both  parents  are  likely  to  pos- 
sess by  inheritance  the  same  imperfections,  which  are 
thus  intensified  in  the  progeny,  while  in  cross-breeding 
the  parents  more  usually  have  different  imperfections 
which  often,  more  or  less,  compensate  each  other  in  the 
immediate  descendants. 

Hybridizing. — As  the  sexual  union  of  quite  different 
kinds  of  animals  sometimes  results  in  the  birth  of  a 
hybrid,  so,  among  plants,  the  ovules  of  one  kind  (spe- 
cies, or  even  genus)  may  be  fertilized  by  the  pollen  of 
another  different  kind,  and  the  seed  thus  developed,  in 
its  growth  produces  a  hybrid  plant.  As  in  the  animal, 
so  in  the  vegetable  kingdom,  the  range  within  which 
hybridization  is  possible  appears  to  be  very  narrow.  It 
is  only  between  rather  closely  allied  plants  that  fecunda- 
tion can  take  place,  and  the  more  close  the  resemblance 
the  more  ready  and  fruitful  the  result.  Wheat,  rye, 
and  barley,  in  ordinary  cultivation,  show  no  tendency  to 
"  mix  ; "  the  pollen  of  one  of  these  similar  plants  rarely 
fertilizing  *  the  ovules  of  the  others.  But  external  sim- 
ilarity is  no  certain  mark  of  capacity  for  hybridization. 
The  apple  and  pear  have  never  yet  been  crossed,  while 
the  almond  and  nectarine  readily  form  hybrids.  (Sachs.) 

Hybrids  are  usually  less  productive  of  seeds  than  the 
parent  plants,  and  sometimes  are  entirely  sterile,  but,  on 
the  other  hand,  they  are  often  more  vigorous  in  their 
vegetative  development — produce  larger  and  more  numer- 
ous leaves,  flowers,  roots,  and  shoots,  and  are  longer- 


*In  the  first  edition  was  written,  "being  incapable  of  fertilizing." 
The  experiments  of  Mr.  Carman  have  lately  shown  that  wheat  and 
rye  may  be  made  to  produce  fertile  hybrids.  A  beardless  wheat  was 
fertilized  by  rye-pollen  and  produced  liine  seeds,  eight  of  which  were 
fully  fertile,  one  nearly  sterile.  The  last  yielded  20  heads,  which  bore 
only  a  few  grains.  The  plants  from  the  nine  fertile  seeds  were  polli- 
nated again  witli  rye  and  produced  but  a  few  fertile  seeds.  A  few 
plants,  seven-eighths  rye,  were  finally  produced,  which  were,  however, 
totally  sterile.  Of  the 'three-fourths "cross,  fertile  progeny  has  been 
raised  for  several  years,  and  the  characters  of  this  genus-hybrid  ap- 
pear to  be  nearly  fixed,  though  occasionally  a  sterile  head  appears.— 
Rural  New  Yorker,  1883,  p.  644. 


324  HOW  CROPS  GROW. 

lived  than  their  progenitors.  For  this  reason  hybrids 
are  much  valued  in  fruit-  and  flower-culture. 

Some  genera  of  plants  have  great  capacity  for  produc- 
ing hybrids.  The  Vine  and  the  Willow  are  striking 
examples.  The  cultivated  Vine  of  Europe  and  Western 
Asia  is  Vitis  vinifera.  In  the  United  States  some 
twelve  distinct  species  are  found,  of  which  three,  Vitis 
riparia,  Vitis  cestivalis,  and  Vitis  labrusca,  are  native  to 
New  England.  Nearly  all  these  kinds  of  grape  cross 
with  such  readiness  that  scores  of  new  hybrids  have  been 
brought  into  cultivation.  "The  kinds  now  known  as 
Clinton,  Taylor,  Elvira,  Franklin,  are  hybrids  of  V. 
riparia  and  V.  labrusca.  York-Madeira,  Eumelan, 
Alvey,  Morton's  Virginia,  Cynthiana,  are  crosses  of  V. 
labrusca  and  V.  cestivalis.  Delaware  is  a  hybrid  of  V. 
labrusca,  V.  vinifera,  and  V.  cestivalis.  Herbemont, 
Rulander,  and  Cunningham  are  hybrids  of  V.  cestivalis, 
V.  cinerea,  and  V.  vinifera.  The  vine  known  in  France 
as  "  Gaston-Bazille  "  is  a  hybrid  of  V.  labrusca,  V.  cesti- 
valis, V.  rupestris,  and  V.  riparia."*  The  foregoing 
are  "spontaneous  wild  hybrids."  The  "Bogers  Seed- 
lings," including  Salem,  Wilder,  Barry,  Agawam,  Mas- 
sasoit,  etc.,  are  examples  of  artificial  hybrids  of  V.  vin- 
ifera and  V.  labrusca. 

Hybridization  between  plants  is  effected,  if  at  all,  by 
removing  from  the  flower  of  one  kind  the  stamens 
before  they  shed  their  pollen,  and  dusting  the  summit 
of  the  properly-matured  pistil  with  pollen  from  another 
kind.  Commonly,  when  two  plants  hybridize,  the  pollen 
of  either  will  fertilize  the  ovules  of  the  other.  In  some 
cases,  however,  two  plants  yield  hybrids  by  only  one 
order  of  connection. 

The  mixing  of  different  Varieties,  as  commonly  hap- 
pens among  maize,  melons,  etc.,  is  not  hybridization, 


*Millardet  in  Saclis's  Lectures  on  the  Physiology  of  Plants,  1887,  p.  786 


325 

in  the  long-established  sense  of  this  word,  but  rather 
"cross-breeding."  The  two  processes  are,  however,  fun- 
damentally the  same,  and  their  results  are  sufficiently 
distinguished  by  the  terms  Species-hybrid,  or  Genus- 
hybrid,  and  Variety-hybrid.  We  are  thus  led  to  brief 
notice  of  the  meaning  of  the  terms  Species  and  Vari- 
ety, and  of  the  distinctions  employed  in  Botanical 
Classification. 

Species. — Until  recently  naturalists  generally  held 
the  view  that  in  "  the  beginning"  certain  kinds  of  plants 
and  animals  were  separately  created,  with  the  power  to 
reproduce  their  own  kind,  but  incapable  of  fertile  hybrid- 
ization, so  that  only  such  original  kinds  could  be  per- 
petuated. Such  supposed  original  kinds  were  called 
Species.  At  present,  on  the  contrary,  most  biologists 
regard  all  existing  kinds  of  plants  and  animals  as  prob- 
ably the  results  of  a  very  slow  and  gradual  development 
or  evolution  from  one  vastly  remote  ancestor  of  the  sim- 
plest type.  On  this  view  a  Plant-Species  comprises  a 
number  of  individuals,  "among  which  we  are  unable  to 
distinguish  greater  differences  than  experience  shows  us 
we  should  find  among  a  number  of  plants  raised  from 
the  seed  of  the  same  parent." 

On  the  former  view,  plants  yielding  fertile  hybrids  or 
crosses  must  be  Varieties  of  the  same  species.  On  the 
latter  view  different  Species  may  hybridize.  They  are 
not  originally  different,  and  by  Evolution  or  Reversion 
may  pass  into  each  other.  On  either  view,  the  distinc- 
tion of  plants  into  species  is  practically  the  same,  being 
largely  a  matter  of  expert  judgment  or  agreement  among 
authorities,  and  not  capable  of  exact  decision  by  refer- 
ence to  fixed  rules  or  known  natural  laws.  The  charac- 
ters that  are  taken  to  be  common  to  all  the  individuals 
of  a  species  are  termed  specific  characters.  The  differ- 
ences used  to  divide  plants  into  species  are  called  specific 
differences. 


HOW  CROPS  GROW. 

Naturalists,  acting  under  the  older  view,  attempted  to 
draw  specific  characters  more  finely  than  is  now  thought 
practicable.  Many  plants  formerly  described  as  separate 
species  are  now  united  together  into  a  single  species, 
the  various  forms  at  first  supposed  to  be  specifically  or 
originally  distinct  having  been  shown  to  be  of  common 
origin,  either  by  producing  them  from  each  other  or  by 
observing  that  they  were  connected  through  a  series  of 
intermediate  forms,  insensibly  grading  into  each  other. 

Varieties. — The  individuals  of  any  "species"  differ. 
In  fact, .no  two  individuals  are  quite  alike.  Circum- 
stances of  climate,  soil,  and  situation  increase  these  dif- 
ferences, and  varieties  originate  when  such  differences 
are  inherited  and  in  the  progeny  assume  a  comparative 
permanence.  But  as  external  conditions  cause  variation 
away  from  any  particular  representative  of  a  species,  so 
they  may  cause  variation  back  again  to  the  original  type. 

Varieties  most  commonly  originate  in  propagation  by 
seed,  especially  in  case  of  the  trees  or  plants  commonly 
cultivated  for  their  fruit.  Seedling  grapes,  apples,  or 
potatoes  are  very  likely  to  differ  from  their  parents. 
Seed  which  has  been  imperfectly  ripened  or  long  kept  is 
said  to  be  prone  to  yield  new  varieties. 

Less  frequently  variations  arise  in  propagation  by 
cuttings,  buds,  grafts,  or  tubers.  Pinks  and  Pelargo- 
niums in  the  florist's  hands  are  prolific  of  these  "sports." 

The  causes  that  produce  varieties  are  probably  numer- 
ous, but  in  many  cases  their  nature  and  their  mode  of 
action  is  obscure  or  unknown.  Scarcity  or  abundance 
of  nutriment,  we  can  easily  comprehend,  may,  on  the  one 
hand,  dwarf  a  plant,  or,  on  the  other,  lead  to  the  pro- 
duction of  a  giant  individual ;  but  how,  in  some  cases, 
the  peculiarities  thus  impressed  upon  individuals  become 
fixed,  and  are  transmitted  to  subsequent  generations, 
while  in  others  they  disappear,  is  difficult  to  explain. 

Varieties  may  often  be  perpetuated  for  a  long  time  by 


REPRODUCTIVE  ORGANS  OF  PLANTS.  327 

the  seed.  This  is  true  of  our  cereal  and  leguminous 
plants,  which  commonly  reproduce  their  kind  with  strik- 
ing regularity.  Varieties  of  some  plants  cannot,  with 
certainty,  be  reproduced  unaltered  by  the  seed,  but  are 
continued  in  the  possession  of  their  peculiarities  by  cut- 
tings, layers,  and  grafts.  The  fact  that  the  seeds  of  a 
potato,  a  grape,  an  apple,  or  pear  cannot  be  depended 
upon  to  reproduce  the  variety,  may  perhaps  be  more 
commonly  due  to  unavoidable  contact  of  pollen  from 
other  varieties  (variety-hybridization)  than  to  inability 
of  the  mother  plant  to  perpetuate  its  peculiarities. 
That  such  inability  often  exists  is,  however,  well  estab- 
lished, and  is,  in  general,  most  obvious  in  case  of  varie- 
ties that  have,  to  the  greatest  degree,  departed  from  the 
original  specific  type  and  of  course,  in  sterile  hybrids. 

The  sports  which  originate  in  the  processes  of  propa- 
gating from  buds  (grafts,  tubers,  cuttings)  are  perpet- 
uated by  the  same  processes. 

Species  and  Varieties,  as  established  in  our  botanical 
literature,  are  exemplified  by  the  Vine,  whose  species  are 
vinifera,  riparia,  Idbrusca,  etc.,  and  some  of  whose 
North  American  Varieties,  the  results  of  hybridization, 
have  already  been  enumerated. 

Genus  (plural  Genera). — Species  which  resemble 
each  other  in  most  important  points  of  structure  are 
grouped  together  by  botanists  into  a  genus.  Thus  the 
various  species  of  oaks, — white,  red,  black,  scrub,  live, 
etc., — taken  together,  form  the  Oak-genus  Quercus, 
which  has  a  series  of  characters  common  to  all  oaks 
(generic  characters),  that  distinguishes  them  from  every 
other  kind  of  tree  or  plant. 

Families,  or  Orders,  in  botanical  language,  are 
groups  of  genera  that  agree  in  certain  particulars.  Thus 
the  several  plants  well-known  as  mallows,  hollyhock, 
okra,  and  cotton,  are  representatives  of  as  many  different 
genera.  They  all  agree  in  a  number  of  points,  especially 


328  HOW  CROPS  GROW. 

as  regards  the  structure  of  their  fruit.  They  are  accord- 
ingly  grouped  together  into  a  natural  family  or  order, 
which  differs  from  all  others. 

Classes,  Series,  and  Classification — Classes  are 
groups  of  orders,  and  Series  are  groups  of  classes.  In 
botanical  classification,  .as  now  universally  employed — 
classification  after  the  Natural  System — all  plants  are 
separated  into  two  series,  as  follows : 

1.  Flowering  Plants  (Phanerogams),  which  produce 
flowers  and  seeds  with  embryos,  and 

2.  Flowerless  Plants   (Cryptogams),   that    have  no 
proper  flowers  nor  seeds,  and  are  reproduced,  in  part, 
by  spores  which  are  in  most  cases  single  cells.     This 
series  includes  Ferns,   Horse-tails,  Mosses,  Liverworts, 
Lichens,  Sea-weeds,  Mushrooms,  and  Molds. 

It  was  believed,  until  recently,  that  there  exists  a  sharp  and  abso- 
lute distinction  between  flowering  and  flowerless  plants,  but  our 
larger  knowledge  now  recognizes  that  here,  as  among  genera,  species, 
and  varieties,  kinds  merge  or  shade  into  each  other. 

The  use  of  Classification  is  to  give  precision  to  our 
notions  and  distinctions,  and  to  facilitate  the  using  and 
acquisition  of  knowledge.  Series,  classes,  orders,  genera, 
species,  and  varieties  are  as  valuable  to  the  naturalist  as 
pigeon-holes  are  to  the  accountant,  or  shelves  and  draw- 
ers to  the  merchant. 

Botanical  Nomenclature. — The  Latin  or  Greek 
names  which  botanists  employ  are  essential  for  the  dis- 
crimination of  plants,  being  equally  received  in  all  coun- 
tries, and  belonging  to  all  languages  where  science  has  a 
home.  They  are  made  necessary,  not  only  by  the  confu- 
sion of  tongues,  but  by  confusions  in  each  vernacular. 

Botanical  usage  requires  for  each  plant  two  names, 
one  to  specify  the  genus,  another  to  indicate  the  species. 
Thus  all  oaks  are  designated  by  the  Latin  word  Quercus, 
while  the  red  oak  is  Quercus  rubra,  the  white  oak  is 
Quercus  alba,  the  live  oak  is  Quercus  virens,  etc. 


REPRODUCTIVE  ORGANS  OF  PLANTS.  329 

The  designation  of  certain  important  families  of  plants 
is  derived  from  a  peculiarity  in  the  form  or  arrangement 
of  the  flower.  Thus  the  pulse  family,  comprising  the 
bean,  pea,  and  vetch,  as  well  as  alfalfa  and  clover,  are 
called  Papilionaceous  plants,  from  the  resemblance  of 
their  flowers  to  a  butterfly  (Latin,  papilio).  Again,  the 
mustard  family,  including  the  radish,  turnip,  cabbage, 
water-cress,  etc.,  are  termed  Cruciferous  plants,  because 
their  flowers  have  four  petals  arranged  like  the  four  arms 
of  a  cross  (Latin,  crux). 

The  flowers  of  a  large  natural  order  of  plants  are 
arranged  side  by  side,  often  in  great  numbers,  on  the 
expanded  extremity  of  the  flower  stem.  Examples  are 
the  thistle,  dandelion,  sunflower,  artichoke,  China-aster, 
etc.,  which,  from  bearing  such  compound  heads,  are 
called  Composite  plants. 

The  Coniferous  (cone-bearing)  plants  comprise  the 
pines,  spruces,  larches,  hemlocks,  etc.,  whose  flowers  are 
arranged  in  conical  receptacles. 

The  flowers  of  the  carrot,  parsnip,  and  caraway  are 
stationed  at  the  extremities  of  stalks  which  radiate  from 
a  central  stem  like  the  arms  of  an  umbrella  ;  hence  they 
are  called  Umbelliferous  plants  (from  umbel,  Latin  for 
little  screen). 

§3. 

THE  FRUIT. 

THE  FRUIT  comprises  the  seed-vessel  and  the  seeds,  to- 
gether with  their  various  appendages. 

Fruits  are  either  dehiscent  when  the  seed-vessel  opens 
and  sheds  the  seed  or  are  indehiscent  when  it  remains 
closed. 

The  seed-vessel,  consisting  of  the  base  of  the  pistil  in 
its  matured  state,  exhibits  a  great  variety  of  forms  and 
characters,  which  serve,  chiefly,  to  define  the  different 


330  HOW   CROPS   GROW. 

kinds  of  Fruits.  Of  these  we  shall  only  adduce  such  as 
are  of  common  occurrence  and  belong  to  the  farm. 

The  Nut  has  a  hard,  leathery  or  bony  indehiscent 
shell,  that  usually  contains  a  single  seed.  Examples  are 
the  acorn,  chestnut,  beech-nut,  and  hazel-nut.  The  cup 
of  the  acorn  and  the  bur  or  shuck  of  the  others  is  a  sort 
of  fleshy  calyx. 

The  Stone-fruit,  or  Drupe,  is  a  nut  enveloped  by  a 
fleshy  or  leathery  coating,  like  the  peach,  cherry,  and 
plum,  also  the  butternut  and  hickory-nut.  Raspberries 
and  blackberries  are  clusters  of  small  drupes. 

Pome  is  a  term  applied  to  fruits  like  the  apple  and 
pear,  the  core  of  which  is  the  true  seed-vessel,  originally 
belonging  to  the  pistil,  while  the  often  edible  flesh  is  the 
enormously  enlarged  and  thickened  calyx,  whose  with- 
ered tips  are  always  to  be  found  at  the  end  opposite  the 
stem. 

The  Berry  is  a  many-seeded  fruit  of  which  the  entire 
seed-vessel  becomes  thick  and  soft,  as  the  grape,  currant, 
tomato,  and  huckleberry. 

Gourd  fruits  have  externally  a  hard  rind,  but  are 
fleshy  in  the  interior.  The  melon,  squash,  and  cucum- 
ber are  of  this  kind. 

The  Akene  is  a  fruit  containing  a  single  seed  which 
does  not  separate  from  its  dry  envelop.  The  so-called 
seeds  of  the  composite  plants — for  example,  the  sunflower, 
thistle,  and  dandelion — are  alcenes.  On  removing  the 
outer  husk  or  seed-vessel  we  find  within  the  true  seed,, 
Many  akenes  are  furnished  with  a  pappus,  a  downy  or 
hairy  appendage,  the  remains  of  the  calyx,  as  seen  in  the 
thistle,  which  enables  the  seed  to  float  and  be  carried 
about  in  the  wind.  The  fruit  or  grain  of  buckwheat  is 
akene-like. 

The  Grains  are  properly  fruits.  Wheat,  rye,  and 
maize  consist  of  the  seed  and  the  seed-vessel  closely 
united.  When  these  grains  are  ground,  the  bran  that 


BEPKODUCTIVE  ORGANS  OF  PLANTS.  331 

comes  off  is  the  seed-vessel  together  with  the  outer  coat- 
ings of  the  seed.  Barley-grain,  in  addition  to  the  seed- 
vessel,  has  the  petals  of  the  flower  or  inner  chaff,  and 
oats  have,  besides  these,  the  calyx  or  outer  chaff  adher- 
ing to  the  seed. 

Pod  is  the  name  properly  applied  to  any  dry  seed-ves- 
sel which  opens  and  scatters  its  seeds  when  ripe.  Sev- 
eral kinds  have  received  special  designations ;  of  these 
we  need  only  notice  one. 

The  Legume  is  a  pod,  like  that  of  the  bean,  which 
splits  into  two  halves,  along  whose  inner  edges  seeds  are 
borne.  The  pulse  family,  or  papilionaceous  plants,  are 
also  termed  leguminous,  from  the  form  of  their  fruit. 

THE  SEED,  or  ripened  ovule,  is  borne  on  a  stalk  which 
connects  it  with  the  seed-vessel.  Through  this  stalk  it 
is  supplied  with  nutriment  while  growing.  When  ma- 
tured and  detached,  a  scar  commonly  indicates  the  point 
of  former  connection. 

The  seed  has  usually  two  distinct  coats  or  integuments. 
The  outer  one  is  often  hard,  and  is  generally  smooth. 
In  the  case  of  cotton-seed  it  is  covered  with  the  valuable 
cotton  fiber.  The  second  coat  is  commonly  thin  and 
delicate. 

The  Kernel  lies  within  the  integuments.  In  many 
cases  it  consists  exclusively  of  the  embryo,  or  rudimen- 
tary plant.  In  others  it  contains,  besides  the  embryo, 
what  has  received  the  name  of  endosperm. 

The  Endosperm  forms  the  chief  bulk  of  all  the 
grains.  If  we  cut  a  seed  of  maize  in  two  lengthwise,  we 
observe,  extending  from  the  point  where  it  was  attached 
to  the  cob,  the  soft  "  chit,"  b,  Fig.  63,  which  is  the  em- 
bryo, to  be  presently  noticed.  The  remainder  of  the 
kernel,  a,  is  endosperm  ;  the  latter,  therefore,  yields  in 
great  part  the  flour  or  meal  which  is  so  important  a  part 
of  the  food  of  man  and  animals. 

The  endosperm  is  intended  for  the  support  of  the 


332  HOW  CROPS  GROW. 

young  plant  as  it  develops  from  the  embryo,  before  it  is 
capable  of  depending  on  the  soil  and  atmosphere  for  sus- 
tenance. It  is  not,  however,  an  indispensable  part  of  the 
seed,  and  may  be  entirely  removed  from  it,  without 
thereby  preventing  the  growth  of  a  new  plant. 

The  Embryo,  or  Germ,  is  the  essential  and  most 
important  portion  of  the  seed.  It  is,  in  fact,  a  ready- 
formed  plant  in  miniature,  and  has  its  root,  stem,  leaves, 
and  a  bud,  although  these  organs  are  often  as  undevel- 
oped in  form  as  they  are  in  size. 

As  above  mentioned,  the  chit  of  the  seeds  of  maize  and 
the  other  grains  is  the  embryo.  Its  form  is  with  diffi- 
culty distinguishable  in  the  dry  seeds,  but  when  they 
have  been  soaked  for  several  days  in  water,  it  is  readily 
removed  from  the  accompanying  endosperm,  and  plainly 
exhibits  its  three  parts,  viz.,  the  Radicle,  the  Plumule, 
and  the  Cotyledon. 

In  Fig.  63  is  represented  the  embryo  of  maize.  In  A 
and  B  it  is  seen  in  section  imbedded  in  the  endosperm. 
C  exhibits  the  detached  embryo.  The  Radicle,  r,  is  the 
stem  of  the  seed-plant,  its  lower  extremity  is  the  point 
from  which  downward  growth  proceeds,  and  from  which 
the  first  true  roots  are  produced.  The  Plumule,  c,  is 
the  central  bud,  out  of  which  the  stem,  with  new  leaves, 
flowers,  etc.,  is  developed.  The  Cotyledon,  b,  is  in 
structure  a  ready-formed  leaf,  which  clasps  the  plumule 
in  the  embryo,  as  the 
proper  leaves  clasp  the 
stem  in  the  mature 
maize-plant.  The  coty- 
ledon of  maize  does  not, 
however,  perform  the 
functions  of  a  leaf;  on 

the  contrary,  it  remains  in  the  soil  during  the  act  of 
sprouting,  and  its  contents,  like  those  of  the  endosperm, 
are  absorbed  by  the  seedling.  The  first  leaves  which  ap- 


BEPBODUCTIVE  ORGANS  OP  PLANTS.  333 

pear  above-ground,  in  the  case  of  maize  and  the  other 
grains  (buckwheat  excepted),  are  those  which  in  the 
embryo  were  wrapped  together  in  the  plumule,  where 
they  can  be  plainly  distinguished  by  the  aid  of  a  mag- 
nifier. 

It  will  be  noticed  that  the  true  grains  (which  have 
sheathing  leaves  and  hollow  jointed  stems)  are  monocot- 
yledonous  (one-cotyledoned)  in  the  seed.  As  has  been 
mentioned,  this  is  characteristic  of  plants  with  endoge- 
nous or  inside-growing  stems  (p.  290). 

The  seeds  of  the  Exogens  (outside-growers — p.  296)  are 
dicotyledonous,  i.  e.,  have  two  cotyledons.  Those  of 
buckwheat,  flax,  and  tobacco  contain  an  endosperm. 
The  seeds  of  nearly  all  other  exogenous  agricultural 
plants  are  destitute  of  an  endosperm,  and,  exclusive  of 
the  coats,  consist  entirely  of  embryo.  Such  are  the  seeds 
of  the  Leguminosae,  viz. ,  the  bean,  pea,  and  clover ;  of 
the  Cruciferae,  viz.,  turnip,  radish,  and  cabbage  ;  of  ordi- 
nary fruits,  the  apple,  pear,  cherry,  plum,  and  peach ;  of 
the  Gourd  family,  viz.,  the  pumpkin,  melon  and  cucum- 
ber; and  finally  of  many  hard- wooded  trees,  viz.,  the 
oak,  maple,  elm,  birch,  and  beech. 

We  may  best  observe  the  structure  of  the  two-cotyle- 
doned  embryo  in  the  ordinary  garden-  or  kidney-bean. 
After  a  bean  has  been  soaked  in  warm  water  for  several 
hours,  the  coats  may  be  easily  removed,  and  the  two 
fleshy  cotyledons,  c,  c,  in  Fig.  64,  are  found  separated 
from  each  other  save  at  the  point  where  the  radicle,  a,  is 
seen  projecting  like  a  blunt  spur.  On 
carefully  breaking  away  one  of  the  coty- 
ledons, we  get  a  side  view  of  the  radicle, 
a,  and  plumule,  J,  the  former  of  which 
/a  was  partially  and  the  latter  entirely  im- 
bedded between  the  cotyledons.  The 
Fig.  64.  plumule  plainly  exhibits  two  delicate 

leaves,  on  which  the  unaided  eye  may  note  the  veins. 


334  HOW  CROPS  GROW. 

These  leaves  are  folded  together  along  their  mid-ribs,  and 
may  be  opened  and  spread  out  with  help  of  a  needle. 

When  the  kidney-bean  (Phaseohis)  germinates,  the 
cotyledons  are  carried  up  into  the  air,  where  they  become 
green  and  constitute  the  first  pair  of  leaves  of  the  new 
plant.  The  second  pair  are  the  tiny  leaves  of  the  plum- 
ule just  described,  between  which  is  the  bud,  whence  all 
the  subsequent  aerial  organs  develop  in  succession. 

In  the  horse-bean  ( Vicia  faba),  as  in  the  pea,  the  cot- 
yledons never  assume  the  office  of  leaves,  but  remain  in 
the  soil  and  gradually  yield  a  large  share  of  their  con- 
tents to  the  growing  plant,  shriveling  and  shrinking 
greatly  in  bulk,  and  finally  falling  away  and  passing  into 
decay. 

b  3. 

VITALITY    OF    SEEDS    AND    THEIR    INFLUENCE    ON    THE 
PLANTS    THEY   PRODUCE. 

Duration  of  Vitality. — In  the  mature  seed  the  em- 
bryo lies  dormant.  The  duration  of  its  vitality  is  very 
various.  The  seeds  of  the  willow,  it  is  asserted,  will  not 
grow  after  having  once  become  dry,  but  must  be  sown 
when  fresh  ;  they  lose  their  germinative  power  in  two 
weeks  after  ripening. 

On  the  other  hand,  single  seeds  of  various  plants,  as  of 
sorrel  (Oxalis  stricta),  shepherd's  purse  (Thlaspi  arv- 
ense),  and  especially  of  trees  like  the  oak,  beech,  and 
cherry,  remain  with  moist  embryos  many  months  or  sev- 
eral years  before  sprouting.  (Nobbe  &  Haenlein,  Vs. 
St.,  XX,  p.  79.) 

Among  the  seeds  of  various  plants,  clover  for  example, 
which,  under  favorable  circumstances,  mostly  germinate 
within  one  or  two  weeks,  may  often  be  found  a  number 
which  remain  unchanged,  sound  and  dry  within,  for 
months  or  years,  though  constantly  wet  externally.  The 


EEPBOBUGTIVE  OEGAHS  OF  PLAKTS.  335 

outer  coat  of  these  seeds  is  exceptionally  thick,  dense, 
and  resistant  to  moisture.  If  this  coat  be  broken  by  the 
scratch  of  a  needle  the  seed  will  shortly  germinate.  In  a 
collection  of  such  seeds,  kept  in  water,  individuals  sprout 
from  time  to  time.  In  case  of  common  sorrel  (Rumex 
acetosella),  Nobbe  &  Haenlein  found  that  10  per  cent  of 
the  seeds  germinated  between  the  400th  and  500th  day 
of  keeping  in  the  sprouting  apparatus. 

The  appearance  of  strange  plants  in  earth  newly 
thrown  out  of  excavations  may  be  due  to  the  presence  of 
such  resistant  seed,  which,  scratched  by  the  friction  of 
the  soil  in  digging,  are  brought  to  germination  after  a 
long  period  of  rest.  Lyell  states  that  seeds  of  the  yellow 
Nelumbo  (water  lily)  have  sprouted  after  being  in  the 
ground  for  a  century,  and  R.  Brown  is  authentically 
said  to  have  germinated  seeds  of  a  Nelumbo  taken  by 
him  from  Hans  Sloane's  herbarium,  where  they  had  been 
kept  dry  for  at  least  150  years. 

The  seeds  of  wheat  usually,  for  the  most  part,  lose  their 
power  of  growth  after  having  been  kept  from  three  to 
seven  years.  Count  Sternberg  and  others  are  said  to 
have  succeeded  in  germinating  wheat  taken  from  an 
Egyptian  mummy,  but  only  after  soaking  it  in  oil. 
Sternberg  relates  that  this  ancient  wheat  manifested  no 
vitality  when  placed  in  the  soil  under  ordinary  circum- 
stances, nor  even  when  submitted  to  the  action  of  acids 
or  other  substances  which  gardeners  sometimes  employ 
with  a  view  to  promote  sprouting. 

Girardin  claims  to  have  sprouted  beans  that  were  over 
a  century  old.  It  is  said  that  Grimstone  with  great  pains 
raised  peas  from  a  seed  taken  from  a  sealed  vase  found  in 
the  sarcophagus  of  an  Egyptian  mummy,  presented  to 
the  British  Museum  by  Sir  G.  Wilkinson,  and  estimated 
to  be  near  3,000  years  old. 

Vilmorin,  from  his  own  trials,  doubts  altogether  the 
authenticity  of  the  "  mummy  wheat,"  and  it  is  probable 


336  HOW  CROPS  GBOW. 

that  those  who  have  raised  mummy  wheat  or  mummy 
peas  were  deceived  either  by  an  admixture  of  fresh  seed 
with  the  ancient,  or  by  planting  in  ordinary  soil,  which 
commonly  contains  a  variety  of  recent  seeds  that  come 
to  light  under  favorable  conditions. 

Dietrich  (Hoff.  Jahr.,  1862-3,  p.  77)  experimented 
with  seeds  of  wheat,  rye,  and  a  species  of  Bromus,  which 
were  185  years  old.  Nearly  every  means  reputed  to  favor 
germination  was  employed,  but  without  success.  After 
proper  exposure  to  moisture,  the  place  of  the  germ  was 
usually  found  to  be  occupied  by  a  slimy,  putrefying  liq- 
uid. Commonly,  among  the  freshest  seeds,  when  put  to 
the  sprouting  trial,  some  will  mold  or  putrefy. 

The  fact  appears  to  be  that  the  circumstances  under 
which  the  seed  is  kept  greatly  influence  the  duration  of 
its  vitality.  If  seeds,  when  first  gathered,  be  thoroughly 
dried,  and  then  sealed  up  in  air-tight  vessels,  there  is  no 
evident  reason  why  their  vitality  should  not  endure  for 
long  periods.  Moisture  and  the  microbes  that  flourish 
where  it  is  present,  not  to  mention  insects,  are  the  agen- 
cies that  usually  put  a  speedy  limit  to  the  duration  of 
the  germinative  power  of  seeds. 

In  agriculture  it  is  a  general  rule  that  the  newer  the 
seed  the  better  the  results  of  its  use.  Experiments  have 
proved  that  the  older  the  seed  the  more  numerous  the 
failures  to  germinate,  and  the  weaker  the  plants  it  pro- 
duces. 

Londet  made  trials  in  1856-7  with  seed-wheat  of  the 
years  1856,  '55,  '54,  and  '53.  The  following  table  exhib- 
its the  results  : 

Number  of  stalks 

Per  cent  of  seeds  Length  of  leavet  four  days  andearsper 

sprouted.  after  coming  up.  hundred  seeds. 

Seed  of  1853 none 

"      "  1854 51  0.4  to  0.8  inches.  269 

"      "   1855 73  1.2        "  365 

"      "  1856 74  1.6       "  404 

The  results  of  similar  experiments  made  by  Haberlandt 
on  various  grains  are  contained  in  the  following  table : 


REPRODUCTIVE  ORGANS  OF  PLANTS.      33? 

Percent  of  seeds  that  germinated  in  1861  from  the  years: 

1850       1851       1854       1855       1857       1858       1859  1860 

Wheat 008473608496 

Rye 0            000              0            0            48  100 

Barley 0             024             0             4833             92  89 

Oats 60              0           56            48              72            32             80  96 

Maize 0    nottried     76          56    not  tried     77           100  97 

Results  of  the  Use   of   Long-kept   Seeds. — The 

fact  that  old  seeds  yield  weak  plants  is  taken  advantage 
of  by  the  florist  in  producing  new  varieties.  It  is  said 
that  while  the  one-year-old  seeds  of  Ten-weeks  Stocks 
yield  single  flowers,  those  which  have  been  kept  four 
years  give  mostly  double  flowers. 

In  case  of  melons,  the  experience  of  gardeners  goes 
to  show  that  seeds  which  have  been  kept  several,  even 
seven  years,  though  less  certain  to  come  up,  yield  plants 
that  give  the  greatest  returns  of  fruit ;  while  plantings 
of  new  seeds  run  excessively  to  vines. 

Unripe  Seeds — Experiments  by  Lucanus  prove  that 
seeds  gathered  while  still  unripe, — when  the  kernel  is 
soft  and  milky,  or,  in  case  of  cereals,  even  before  starch 
has  formed,  and  when  the  juice  of  the  kernel  is  like 
water  in  appearance, — are  nevertheless  capable  of  germi- 
nation, especially  if  they  be  allowed  to  dry  in  connection 
with  the  stem  (after-ripening).  Such  immature  seeds, 
however,  have  less  vigorous  germinative  power  than 
those  which  are  allowed  to  mature  perfectly  ;  when  sown, 
many  of  them  fail  to  come  up,  and  those  which  do,  yield 
comparatively  weak  plants  at  first  and  in  poor  soil  give  a 
poorer  harvest  than  well-ripened  seed.  In  rich  soil, 
however,  the  plants  which  do  appear  from  unripe  seed, 
may,  in  time,  become  as  vigorous  as  any.  (Lucanus,  Vs. 
St.,  IV,  p.  253.) 

According  to  Siegert,  the  sowing  of  unripe  peas  tends 
to  produce  earlier  varieties.  Liebig  says:  "The  gar- 
dener is  aware  that  the  flat  and  shining  seeds  in  the  pod 
of  the  Stock  Gillyflower  will  give  tall  plants  with  single 
flowers,  while  the  shriveled  seeds  will  furnish  low  plants 
with  double  flowers  throughout.  22 


338  HOW  CROPS  GROW. 

Cohn  found  that  seeds  not  fully  ripe  germinate  some- 
what sooner  than  those  which  are  more  mature,  and  he 
believes  that  seeds  in  a  medium  stage  of  ripeness  germi- 
nate most  readily. 

Quick-  and  Slow-Sprouting  Seeds. — When  a  con- 
siderable number  of  agricultural  or  garden  seeds,  fresh 
and  of  uniform  appearance,  are  placed  under  favorable 
circumstances  for  germinating,  it  is  usually  observed 
that  sprouting  begins  within  two  to  ten  days,  and  con- 
tinues for  one  or  several  weeks  before  all  or  nearly  all 
the  living  embryos  have  manifestly  commenced  to  grow. 
Nobbe  (in  1886  and  1887)  found  in  extensive  trials  with 
12  varieties  of  stocks,  Matthiola  annua,  that  the  quick- 
sprouting  seeds,  which  germinated  in  three  to  four  days, 
yielded  earlier  and  larger  plants,  which  blossomed  with 
greater  regularity  and  certainty,  and  produced  a  pre- 
ponderance (82  per  cent)  of  sterile  double  flowers,  while 
the  slow-sprouting  seeds,  that  were  ten  to  twelve  days  in 
germinating,  gave  smaller  plants  that  came  later  to 
bloom,  and  yielded  73  per  cent  of  fertile  single  flowers. 

Should  continued  trials  prove  these  results  to  be  of 
constant  occurrence,  it  is  evident  that  by  breeding  exclu- 
sively from  the  quick-sprouting  seeds,  the  double-flower- 
ing varieties  should  soon  become  extinct,  from  failure  to 
produce  seed.  On  the  other  hand,  exclusive  use  of  the 
slow-sprouting  seeds  would  extinguish  the  tendency  to 
variation  and  double-blooming,  which  gives  this  plant 
its  value  to  the  florist. 

Dwarfed  or  Light  Seeds. — Miiller,  as  well  as  Hell- 
riegel,  found  in  case  of  the  cereals  that  light  or  small 
grain  sprouts  quicker  but  yields  weaker  plants,  and  is 
not  so  sure  of  germinating  as  heavy  grain. 

Liebig  asserts  (Natural  Laws  of  Husbandry,  Am. 
Ed.,  1863,  p.  24)  that  "poor  and  sickly  seeds  will  pro- 
duce stunted  plants,  which  will  again  yield  seeds  bearing 
in  a  great  measure  the  same  character."  This  is  true 
"in  the  long  run,"  i.  e.,  small  or  light  seeds,  the  result 


REPRODUCTIVE  ORGANS  OF  PLANTS.  339 

of  unfavorable  conditions,  will,  under  the  continuance 
of  those  conditions,  produce  stunted  plants  (varieties), 
whose  seeds  will  be  small  and  light.  (Compare  Tuscan 
and  pedigree  wheat,  p.  158.) 

Schubart,  whose  observations  on  the  roots  of  agricul- 
tural plants  are  detailed  in  a  former  chapter  (p.  263), 
says,  as  the  result  of  much  investigation,  "  the  vigorous 
development  of  plants  depends  far  less  upon  the  size  and 
weight  of  the  seed  than  upon  the  depth  to  which  it  is 
covered  with  earth,  and  upon  the  stores  of  nourishment 
which  it  finds  in  its  first  period  of  life."  Reference  is 
here  had  to  the  immediate  produce  under  ordinary  agri- 
cultural conditions. 

Value  of  Seed  as  Related  to  its  Density. — From 
a  series  of  experiments  made  at  the  Eoyal  Agricultural 
College  at  Cirencester,  in  1863-6,  Church  concludes  that 
the  value  of  seed-wheat  stands  in  a  certain  connection 
with  its  specific  gravity  (Practice  with  Science,  pp.  107, 
342,  345,  London,  1867).  He  found  :— 

1.  That  seed- wheat  of  the  greatest  density  produces 
the  densest  seed. 

2.  The  seed-wheat  of  the  greatest  density  yields  the 
greatest  amount  of  dressed  corn. 

3.  The  seed-wheat  of  medium  density  generally  gives 
the  largest  number  of  ears,  but  the  ears  are  poorer  than 
those  of  the  densest  seed. 

4.  The  seed-wheat  of  medium  density  generally  pro- 
duces the  largest  number  of  fruiting  plants. 

5.  The  seed-wheats  which  sink  in  water,  but  float  in  a 
liquid  having  the  specific  gravity  1.247,  are  of  very  low 
value,  yielding,  on  an  average,  but  34.4  Ibs.  of  dressed 
grain  for  every  100  yielded  by  the  densest  seed. 

6.  The  densest  wheat-seeds  are  the  most  translucent 
or  horny,  and  contain  about  one-fourth  more  proteids 
(or  3  per  cent  more)  than  the  opake  or  starchy  grains 
from  the  same  kind  of  wheat,  or  even  from  the  same 
individual  plant,  or  even  from  the  same  ear. 


340  SOW  CEOPS  GEOW. 

• 

7.  The  weight  of  wheat  per  bushel  depends  upon 
many  circumstances,  and  bears  no  constant  relation  to 
the  density  of  the  seed. 

The  densest  grains  are  not,  according  to  Church, 
always  the  largest.  The  seeds  he  experimented  with 
ranged  from  sp.  gr.  1.354  to  1.401. 

Marek  has  shown  that  specific  gravity  is  no  universal 
test  of  the  quality  of  seed,  for  while,  in  case  of  wheat, 
flax,  and  colza,  the  large  seeds  are  generally  the  denser, 
the  reverse  is  true  of  horse-beans  (  Vicia  faba)  and  peas 
(F*.  St.,  XIX,  40). 

The  Absolute  .Weight  of  Seeds  from  different 
varieties  of  the  same  species  is  known  to  vary  greatly, 
as  is  well  exemplified  by  comparing  the  kernels  of  com- 
mon field  maize  with  those  of  "pop  corn."  Similar  dif- 
ferences are  also  observable  in  different  single  seeds  from 
the  same  plant,  or  even  from  the  same  pod  or  ear.  Thus, 
Harz  obtained  what  were,  to  all  appearance,  normally 
developed  seeds  that  varied  in  weight  as  follows  : 

FROM  SINGLE  PLANTS.  Milligrams. 

Wheat,  Triticum  vidgare,  from  15  to  37 

Wheat,  Triticum  polonicum,  «  21  to   55 

Barley,  Hordeum  distichon,  M  31  to    41 

Oats,  Avena  sativa,  «        jg  to  30 

Maize,  Zea  Mays  cinquantino,  ««  169  to  201 

Pea,  Pisum  sativum,  «  543  to  ggg 

FROM  SINGLE  FRUIT  (PODS). 

Pea> ....from  309  to  473 

Vetch, .<       33  to    66 

Lupin, ««       486  to  639 

Differences  often  no  less  marked  are  found  among  the 
seeds  in  any  considerable  sample,  gathered  from  a  large 
number  of  plants  and  representing  a  crop.  Nobbe,  with 
great  painstaking,  has  ascertained  the  average,  maxi- 
mum and  minimum  weights,  of  180  kinds  of  seeds,  such 
as  are  found  in  commerce  or  are  used  in  Agriculture, 
Horticulture,  and  Forestry.  The  following  table  gives 
some  of  his  results  : 


EEPEODUCTIVE  ORGANS  OF  PLANTS. 


341 


Absolute  Weight  of  Commercial  Seeds. 

Number  of  Weight  of  one  Seed  in 
Samples                       Milligrams. 

Examined.  Average.  Maximum.  Minimum! 

Oats, 84  28.8  54.1  14.7 

Barley, 66  41.0  48.9  27.7 

Rye,... 119  23.3  47.9  13.0 

Wheat, 96  37.6  45.8  15.2 

Maize, 22  282.7  382.9  114.5 

Beet, 39  22.0  42.4  14.2 

Turnip,  Brassica  rapifera,..  23  2.2  3.0              1.4 

Carrot, 35  1.2  1.7                0.8 

Pea, 43  185.8  564.6  46.1 

Kidney  Bean,  Phaseolus 5  585.6  926.3  367.3 

Horse  Bean,  Vicia 7  676.0  2061.0  256.4 

Potato, 3  0.6  0.7               0.5 

Tomato, 5  2.5  2.7               2.4 

Spinage, 4  6.9  9.0                2.4 

Radish, 5  7.1  9.7               5.7 

Lettuce, 18  1.1  1.7               0.8 

Parsnip, 3  3.1  3.8               2.3 

Squash, 5  173.0  322.0  106.7 

Musk  Melon, 3  32.9  35.5  28.2 

Cucumber, 6  25.4  27.0  21.0 

Timothy,  Phleum  pratense,,  73  0.41  0.59             0.34 

Blue  Grass,  Poa  pratensis, . .  28  0.15  0.21             0.10 

Red  Clover, 355  1.60  2.08              1.14 

White  Clover, 53  0.61  0.69             0.47 

Ten-weeks-stocks,     Mattlii- 

ola  annua, 4  1.50  1.60              1.39 

Oak,  Quercus  pedunculata,.  15  2013.4  4213.5  761.6 

It  ia  noteworthy,  that  in  case  of  Oats,  Eye,  Wheat, 
Maize,  Beet,  Spinage,  and  Squash,  the  heaviest  seeds 
weigh  thrice  as  much  as  the  lightest.  With  Turnip, 
Carrot,  Kidney-bean,  Lettuce,  and  Blue  grass,  some 
seeds  are  double  the  weight  of  others.  The  horse-bean 
gives  some  seeds  eight  times  as  heavy  as  others.  The 
differences  brought  out  in  the  Table  in  many  cases  are 
due  to  the  representation  of  different  varieties ;  the 
larger  seeds,  to  some  extent,  belonging  to  larger  plants  ; 
but  the  great  range  of  weight,  noted  with  regard  to  the 
seed  of  the  Oak,  applies  to  15  crops  of  sound  acorns  from 
one  and  the  same  tree,  gathered  in  15  successive  years. 

In  many  varieties  of  Indian  Corn,  the  kernels  at  the 
base  of  the  ear  are  larger,  and  those  at  the  tip  are 
smaller,  than  those  of  the  middle  portion.  Other  varie- 
ties are  characterized  by  great  uniformity  in  the  size  of 
the  kernels,  having  been  "  bred  up  "  to  this  quality  by 
careful  seed-selection. 

It  is  well-known  that  the  middle  part  of  the  ears  of 


342  HOW  CROPS  GROW. 

wheat  and  barley  produce  the  heaviest  kernels.  Nobbe 
numbered  and  weighed  the  spikelets  from  an  ear  of  six- 
rowed  barley  and  from  one  of  winter  wheat.  Either  ear 
contained  27  spikelets,  each  with  three  kernels.  The 
kernels  of  the  smallest  barley-spikelet,  No.  2,  from  the 
base  of  the  ear,  weighed  1.5  milligrams;  those  of  the 
largest,  No.  10,  weighed  103.5  mg.  No.  27  weighed 
32.5  mg.  The  corresponding  numbers  in  wheat  weighed 
0.5,  34.5  and  10.8  mg. 

In  case  of  barley,  each  of  the  first  five  spikelets,  count- 
ing from  the  base,  weighed  less  than  70  milligrams. 
The  6th  to  the  22d,  inclusive,  weighed  75  mg.  or  more. 
The  7th  to  the  16th  weighed  90  mg.  or  more.  The  17th 
to  the  21st,  80  mg.  or  more.  Thence,  to  the  tip,  the 
weight  rapidly  declined  to  about  30  milligrams. 

The  wheat  kernels  exhibited  quite  similar  variation  of 
weight. 

Dividing  the  27  spikelets  into  three  groups  of  nine 
each,  we  have  the  following  comparison  of  weights  of 
seeds,  to  which  is  added  the  total  lengths  of  the  rootlets 
that  were  formed  after  germination  had  gone  on  for  five 


BARLEY.  WHEAT. 

Weight.    Length  of  Root.  Weight.    Length  of  Root. 
Spikelets,   1  to    9     426  mg.  670mm.         153  mg.  223mm. 

10  to  18      828    «  8281     "  282    «  1094     « 

18  to  27      512   «  1364     "  191    "  454     « 

The  seeds  of  the  middle  portion  of  the  ears  of  barley  and 
wheat  are  thus  seen  to  be  very  considerably  heavier  than 
those  of  either  the  base  or  tip,  and  also  show  greater  ger- 
minative  vigor,  as  measured  by  the  comparative  growth 
of  the  roots  in  a  given  short  time. 

The  greater  weight  and  germinative  energy  of  the 
seeds  from  the  middle  of  the  ears,  stand  in  relation  to 
the  fact  that  these  seeds  are  the  oldest — the  flowers  from 
which  they  develop  being  the  first  to  open  and  fructify. 
In  case  of  a  head  of  summer  rye,  Nobbe  found  that  the 


REPRODUCTIVE  ORGANS  OF  PLANTS.  343 

33  spikelets,  each  with  two  buds,  required  a  week  for 
blossoming ;  the  first  of  the  66  flowers  to  open  were 
mostly  those  of  the  thirties  and  forties,  and  the  last 
those  of  the  tens,  fifties,  and  sixties,  counting  from  the 
base  upward.  These  middle  seeds  had  accordingly  an 
earlier  start,  and  better  chance  for  full  development, 
than  those  at  the  base  and  tip  of  the  ear. 

Oat  kernels  usually  grow  in  pairs,  the  upper  one  of 
each  pair  being  in  general  lighter  and  smaller  than  the 
lower  one.  Nobbe  counted  out  200  upper  kernels,  200 
lower  kernels,  and  200  average  kernels,  without  selection. 
These  were  weighed,  and,  after  soaking  In  water  for  24 
hours,  were  placed  in  a  sprouting  apparatus  at  a  tem- 
perature of  about  70°  F.  The  results  were  as  follows  : 

100  seeds          Number  of  seeds  that  sprouted. 

weighed.  On  the  Total  in 

Grams.  3d,  4th,  5th,  6th,  7th,  8th,  9th,  10th  days.  10  days. 
Upper  Kernels,     1.53        2    100    76     15      3      2  1  199 

Lower  Kernels,     3.46      109      75      9       3       2  198 

Average  Kernels,  2.69       45    110    30       8       4       1       1  199 

Here,  as  in  case  of  wheat  and  barley,  the  light  seeds 
were  slower  to  germinate. 

In  general,  it  would  appear  that,  other  things  being 
equal,  stronger  and  more  perfect  plants  and  larger 
crops  are  produced  from  heavy  than  from  small  seeds. 
Many  comparisons  are  on  record  that  have  given  such 
results  ;  not  only  small  trials  in  garden  plats,  but  also 
field  experiments  on  a  larger  scale. 

Lehmann  sowed,  on  each  of  three  plats  of  92  square 
feet,  the  same  number  (528)  of  peas,  of  the  same  kind 
but  of  different  weight,  with  results  as  here  tabulated  • 

Weights  of  100  No.  of  Yield  (grams). 

seed-peas,     plants.  Kernels.  Pods.    Straw.  Total. 

Small  seed-peas,         160  gm.  423  998  280         2010  3288 

Medium  seed-peas,    221    "  478  1495  357         2630  4482 

Large  seed-peas,        273   "  480          1814          437         3170  5421 

Of  the  peas  sown,  there  failed  to  germinate  about  9 


344  HOW  CEOPS  GEOW. 

per  cent,  both  of  the  large  and  medium  sizes,  and  20  per 
cent  of  the  small  ones. 

The  total  produce  from  the  small  seeds  was  less  abun- 
dant in  all  respects  than  that  of  the  medium,  and  this 
less  than  that  of  the  large  seeds. 

Calculated  upon  the  same  number  of  plants,  the  differ- 
ences, though  less  in  degree,  are  still  very  decided  : 

100  Plants  Yielded  Kernels.  Pods.  Straw.  Total. 
From  small  seeds,              236                  66               475  777 

From  medium  seeds,         313  75  550  938 

From  large  seeds,  378  91  660  1129 

Lehmann,  in  another  experiment,  found  that  from  the 
same  weight  of  seed  a  larger  crop  is  given  by  large  seed 
than  by  small,  although  the  number  of  plants  may  be 
considerably  less. 

From  the  same  weight  (188  gin.)  of  seed-peas  were 
produced  : 

Number  of  Weight  of  Kernels 

Seed-peas.    Plants.  per 92 sq.ft.  Per  100 plants. 
By  small  seed,          780               680  1590  234 

By  medium  seed,      530  505  2224  440 

By  large  seed,  384  360  2307  640 

DriesdorfE  sowed  separately,  on  the  same  land,  winter 
wheat,  as  winnowed,  and  the  same  divided  by  sifting  into 
three  sizes.  In  April  and  May  the  vegetation  from  the 
largest  seed  was  evidently  in  advance,  and  at  harvest 
the  relative  yield  for  100  of  unsifted  seed  was  121  from 
the  largest,  105  for  the  medium,  and  95  for  the  smallest 
seed. 

Improved  varieties  are  often  the  result  of  continued 
breeding  from  the  heaviest  or  largest  seeds,  accompanied 
by  high  culture  on  rich  soil,  and  thin  planting,  so  that 
the  roots  have  abundant  earth  for  unhindered  develop- 
ment. 

Hallet,  in  1857,  selected  two  ears  of  Nursery  Wheat, 
"  the  finest  quality  of  red  wheat  grown  in  England,"  con- 
taining, together,  87  grains,  and  planted  the  kernels  12 
inches  apart  every  way.  At  harvest  one  prime  grain 


REPRODUCTIVE  ORGANS  OF  PLANTS.      345 

produced  10  ears,  that  contained  in  the  aggregate  688 
kernels.  The  finest  10  ears  that  could  be  selected  from 
the  whole  produce  of  the  other  86  grains  yielded  but 
598  kernels.  The  79  kernels  of  the  one  best  ear  were 
planted  as  before,  and  the  produce  of  the  finest  seed,  as 
shown  by  the  harvest,  was  used  for  the  next  year's  sow- 
ing. The  results  of  continuing  this  process  of  selection 
are  tabulated  below  : 

Number  of 

Length,  Containing,     ears  on 

Year.                                                               inches.  grains.      finest  stool. 

1857.  Original 4f  47 

1858.  Finest  ear, 6J  79                     10 

1859.  Finest  ear 7|  91                     22 

1860.  Ears  imperfect  from  wet  season, ...  39 

1861.  Finest  ear, gf  123                    52 

In  five  years,  accordingly,  the  length  of  the  ears  was 
doubled,  their  contents  nearly  trebled,  and  the  tillering 
capacity  of  tbe  plant  increased  five-fold.  (Journal  Royal 
Ag.  Soc.,  XXII,  p.  374.) 

Wollny  has  given  account  of  27  garden  trials,  with 
large  and  small  seeds  of  rye,  buckwheat,  beans,  vetches, 
peas,  lupins,  soybeans,  colza,  mustard,  maize,  and  red- 
clover,  on  plats  of  four  square  meters  (43  sq.  ft.),  during 
the  years  1873  to  1880,  with  the  nearly  invariable  results  : 
1,  that  the  quantity  of  crop  increases  with  the  size  of 
the  seed  ;  2,  that  the  large  seed  produces  principally 
large  seed,  and  the  small  seed  small ;  3,  that  the  relative 
productiveness  of  the  small  seed  is  greater  than  that  of 
the  large  ;  and  4,  that  the  vitality  of  the  plants  from 
small  seed  is  usually  less  than  that  of  the  plants  from 
large  seed. 

The  facts  of  experience  fully  justify  the  conclusion 
that,  in  general,  other  things  being  equal,  the  heaviest 
seed  is  the  best. 

Signs  of  Excellence. — So  far  as  the  common  judg- 
ment can  determine  by  external  signs,  the  best  seed  is  that 
which,  on  the  one  hand,  is  large,  plump,  and  heavy,  and  on 


346  HOW  CEOPS  GEOW. 

the  other  is  fresh  or  bright  to  the  eye,  and  free  from 
musty  odor.  The  large,  plump,  and  heavy  seeds  are 
those  which  have  attained  the  fullest  development,  and 
can  best  support  the  embryo  when  it  shall  begin  to 
grow ;  those  fresh  in  color  and  odor  are  likely  to  be  new, 
and  to  have  the  most  vigorous  vitality. 

Ancestry  ;  Race-Vigor  ;  Constancy. — There  are, 
however,  important  qualities  in  seed  that  are  involved  in 
their  heredity  and  give  no  outward  token  of  their  pres- 
ence. Race-vigor  and  Constancy  are  qualities  of  this 
sort,  and  these  wonderfully  persist  in  some  kinds  of  seed 
and  are  lacking  in  others.  All  cultivated  plants  occur 
in  numerous  varieties,  and,  as  the  years  go  on,  older 
varieties  "run  out "  or  are  neglected  and  forgotten,  their 
place  being  taken  by  newer  and  often,  or  for  a  time,  bet- 
ter ones.  It  would  appear  that  a  long  course  of  careful 
cultivation  under  the  most  favorable  and  uniform  condi- 
tions, coupled  with  careful  and  intelligent  selection  of 
seed  from  the  best-developed  plants,  not  only  leads  to 
the  formation  of  the  best  varieties,  but  tends  to  establish 
their  permanence,  so  that  when  soil,  climate,  and  care 
are  unfavorable,  the  kind  maintains  its  character  and 
makes  a  stout  resistance  to  deteriorating  influences. 

In  order  to  properly  appreciate  the  value  of  seed,  its 
Pedigree  must  therefore  be  known.  But  seed  of  ances- 
try, that  has  a  long-established  character  for  certain 
qualities,  in  a  given  locality,  may  prove  of  little  value 
under  widely  different  circumstances,  or,  if  its  products 
be  cultivated  under  new  conditions,  it  may  lose  its  char- 
acteristics more  or  less,  and  develop  into  other  varieties. 
It  is  well  known  that  various  perennial  plants  of  tropical 
climates,  like  the  castor  bean,  become  annuals  in  north- 
ern latitudes,  and  it  may  easily  happen  that  the  seed  of 
some  prized  variety  which  is  of  unquestioned  pedigree,  as 
far  as  the  remote  lines  of  its  descent  can  indicate,  is  of  lit- 
tle worth  in  soils  or  climates  to  which  it  is  unaccustomed, 


REPEODUCTIVE  ORGANS  OF   PLANTS.  347 

from  not  having  the  power  to  transmit  the  specially 
valuable  qualities  of  its  progenitors.  In  high,  northern 
latitudes,  the  summer  cereals  ripen  after  a  short  period 
of  rapid  growth,  but  seed  of  such  grain,  sown  in  the  soil 
of  temperate  regions,  does  not  produce  early  varieties  ;  its 
rate  of  growth,  after  a  few  years  at  most,  is  'governed  by 
the  climate  to  which  it  is  exposed.  In  considering  the 
pedigree  of  seed,  therefore,  it  is  not  merely  the  repute 
or.  characters  of  the  ancestry,  but  the  probability  that 
the  ancestral  excellencies  reside  in  and  will  be  trans- 
mitted by  the  seed,  that  constitutes  the  practical  point. 


DIVISION  III. 
LIFE    OF   THE    PLANT. 

CHAPTER  I. 
GERMINATION. 

§1- 

\ 

INTRODUCTORY. 

Having  traced  the  composition  of  vegetation  from  its 
ultimate  elements  to  the  proximate  organic  compounds, 
and  studied  its  structure  in  the  simple  cell  as  well  as  in 
the  most  highly-developed  plant,  and,  as  far  as  needful, 
explained  the  characters  and  functions  of  its  various 
organs,  we  approach  the  subject  of  VEGETABLE  LIFE 
and  NUTRITION,  and  are  ready  to  inquire  how  the  plant 
increases  in  bulk  and  weight  and  produces  starch,  sugar, 
oil,  albuminoids,  etc.,  which  constitute  directly  or  in- 
directly almost  the  entire  food  of  animals. 

The  beginning  of  the  agricultural  plant  is  in  the 
flower,  at  the  moment  of  fertilization  by  the  action  of  a 
pollen  tube  on  the  contents  of  the  embryo-sack.  Each 
embryo  whose  development  is  thus  ensured  is  a  plant  in 
miniature,  or  rather  an  organism  that  is  capable,  under 
proper  circumstances,  of  unfolding  into  a  plant. 

349 


350  HOW  CEOPS  GROW. 

The  first  process  of  development,  wherein  the  young 
plant  commences  to  manifest  its  separate  life,  and  in 
which  it  is  shaped  into  its  proper  and  peculiar  form,  is 
called  germination. 

The  GENEEAL  PEOCESS  and  CONDITIONS  of  GEEMIN- 
ATION  are  familiar  to  all.  In  agriculture  and  ordinary 
gardening  we  bury  the  ripe  and  sound  seed  a  little  way 
in  the  soil,  and  in  a  few  days,  or  weeks,  it  usually  sprouts, 
provided  it  finds  a  certain  degree  of  warmth  and  moisture. 

Let  us  attend  somewhat  in  detail  first  to  the  phenom- 
ena of  germination  and  afterward  to  the  requirements  of 
the  awakening  seed. 


§2. 


THE  PHENOMENA  OP  GERMINATION. 

The  student  will  do  well  to  watch  with  care  the  various 
stages  of  the  act  of  germination,  as  exhibited  in  several 
species  of  plants.  For  this  purpose  a  dozen  or  more 
seeds  of  each  plant  are  sown,  the  smaller,  one-half,  the 
larger,  one  inch  deep,  in  a  box  of  earth  or  sawdust,  kept 
duly  warm  and  moist,  and  one  or  two  of  each  kind  are 
uncovered  and  dissected  at  successive  intervals  of  12 
hours  until  the  process  is  complete.  In  this  way  it  is 
easy  to  trace  all  the  visible  changes  which  occur  as  the 

•J 

embryo  is  quickened.  The  seeds  of  the  kidney-bean, 
pea,  of  maize,  buckwheat,  and  barley,  may  be  employed. 

We  thus  observe  that  the  seed  first  absorbs  a  large 
amount  of  moisture,  in  consequence  of  which  it  swells 
and  becomes  more  soft.  We  see  the  germ  enlarging  be- 
neath the  seed  coats,  shortly  the  integuments  burst  and 
the  radicle  appears,  afterward  the  plumule  becomes 
manifest. 

In  a1!  agricultural  plants  the  radicle  buries  itself  in 


GEBMINATIOH.  351 

the  soil.  The  plumule  ascends  into  the  atmosphere  and 
seeks  exposure  to  the  direct  light  of  the  sun. 

The  endosperm,  if  the  seed  have  one,  and  in  many 
cases  the  cotyledons  (so  with  the  horse-bean,  pea,  maize, 
and  barley),  remain  in  the  place  where  the  seed  was 
deposited.  In  other  cases  (kidney-bean,  buckwheat, 
squash,  radish,  etc.)  the  cotyledons  ascend  and  become 
the  first  pair  of  leaves. 

The  ascending  plumule  shortly  unfolds  new  leaves, 
and,  if  coming  from  the  seed  of  a  branched  plant,  lateral 
buds  make  their  appearance.  The  radicle  divides  and 
subdivides  in  beginning  the  issue  of  true  roots. 

When  the  plantlet  ceases  to  derive  nourishment  from 
the  mother-seed  the  process  is  finished. 

§3. 

THE  CONDITIONS  OP  GEEMINATION. 

As  ta  the  Conditions  of  Germination  we  have  to  con- 
sider in  detail  the  following  : — 

a.  Temperature. — Seeds  sprout  within  certain  more 
or  less  narrow  limits  of  warmth. 

Sachs  has  approximately  ascertained,  for  various  agri- 
cultural seeds,  the  limits  of  warmth  at  which  germina- 
tion is  possible.  The  lowest  temperatures  range  from 
below  40°  to  55°,  the  highest,  from  102°  to  116°.  Below 
the  minimum  temperature  a  seed  preserves  its  vitality, 
above  the  maximum  it  is  killed.  He  finds,  likewise,  that 
the  point  at  which  the  most  rapid  germination  occurs  is 
intermediate  between  these  two  extremes,  and  lies  be- 
tween 79°  and  93°.  Either  elevation  or  reduction  of 
temperature  from  these  degrees  retards  the  act  of 
sprouting. 

In  the  following  table  are  given  the  special  tempera* 
tures  for  six  common  plants  : 


352  HOW  CROPS  GROW. 

Lowest  Highest  Temperature  of  most 

Temperature.  Temperature,  rapid  Germination. 

Wheat,*                               40°  F.  104°  F.  84°  F.   - 

Barley,                                 41  104  84 

Pea,                                       44.5  102  84 

Maize,                                  48  115  93 

Scarlet-bean,                    49  ill  79 

Squash,                                54  115  93 

For  the  agricultural  plants  cultivated  in  New  England, 
a  range  of  temperature  of  from  55°  to  90°  is  adapted  for 
healthy  and  speedy  germination. 

It  will  be  noticed  in  the  above  Table  that  the  seeds  of 
plants  introduced  into  northern  latitudes  from  tropical 
regions,  as  the  squash,  bean,  and  maize,  require  and 
endure  higher  temperatures  than  those  native  to  temper- 
ate latitudes,  like  wheat  and  barley.  The  extremes  given 
above  are  by  no  means  so  wide  as  would  be  found  were 
we  to  experiment  with  other  plants.  Some  seeds  will 
germinate  near  32°,  the  freezing  point  of  water,  as  is 
true  of  wheat,  rye,  and  water-cress,  as  well  as  of  various 
alpine  plants  that  grow  in  soil  wet  with  the  constant 
drip  from  melting  ice.  On  the  other  hand,  the  cocoa- 
nut  is  said  to  yield  seedlings  with  greatest  certainty  when 
the  heat  of  the  soil  is  120°. 

Sachs  has  observed  that  the  temperature  at  which 
germination  takes  place  materially  influences  the  relative 
development  of  the  parts,  and  thus  the  form,  of  the  seed- 
ling. Very  low  temperatures  retard  the  production  of 
new  rootlets,  buds,  and  leaves.  The  rootlets  which  are 
rudimentary  in  the  embryo  become,  however,  very  long. 
On  the  other  hand,  very  high  temperatures  cause  the 
rapid  formation  of  new  roots  and  leaves,  even  before 
those  existing  in  the  germ  are  fully  unfolded.  The 
medium  and  most  favorable  temperatures  bring  the 
parts  of  the  embryo  first  into  development,  at  the  same 
time  the  rudiments  of  new  organs  are  formed  which  are 
afterwards  to  unfold. 


*  Wheat,  and  probably  barley,  may,  occasionally,  germinate  at,  or 
very  near,  32°. 


GEBMINATION.  353 

6.  Moisture. — A  certain  amount  of  moisture  is  indis- 
pensable to  all  growth.  In  germination  it  is  needful 
that  the  seed  should  absorb  water  so  that  motion  of  the 
contents  of  the  germ-cells  can  take  place.  Until  the 
seed  is  more  or  less  imbued  with  moisture,  no  signs  of 
sprouting  are  manifested,  and  if  a  half-sprouted  seed 
be  allowed  to  dry  the  process  of  growth  is  effectually 
checked. 

The  degree  of  moisture  different  seeds  will  endure  or 
require  is  exceedingly  various.  The  seeds  of  aquatic 
plants  naturally  germinate  when  immersed  in  water. 
The  seeds  of  most  agricultural  plants,  indeed,  will 
quicken  under  water,  but  they  germinate  most  health- 
fully when  moist  but  not  wet.  Excess  of  water  often 
causes  seeds  to  rot. 

c.  Oxygen  Gas. — Free  Oxygen,  as  contained  in  the 
air,  is  likewise  essential.     Saussure  demonstrated  by  ex- 
periment that  proper  germination  is  impossible  in  its 
absence,  and  cannot  proceed  in  an  atmosphere  of  other 
gases.     The  chemical  activity  of  oxygen  appears  to  be 
the  means  of  exciting  the  growth  of  the  embryo. 

d.  Light. — It  has  been  erroneously  taught  that  light 
is  prejudicial  to  germination,  and  that  therefore  seed 
must  be  covered.     (Johnston's  Lectures  on  Ag.  Chem.  & 
Geology,  2d  Eng.  Ed.,  pp  226  and  227.)     Nature  does 
not  bury  seeds,  but  scatters  them  on  the  surface  of  the 
ground  of  forest  and  prairie,  where  they  are,  at  the  most, 
half -covered  and  by  no  means  removed  from  the  light. 
The  warm  and  moist  forests  of  tropical  regions,  which, 
though  shaded,  are  by  no  means  dark,  are  covered  with 
sprouting  seeds.     The  seeds  of  heaths,  calceolarias,  and 
some  other  ornamental  plants,  germinate  best  when  un- 
covered, and  the  seeds  of  common  agricultural  plants 
will  sprout  when  placed  on  moist  sand  or  sawdust,  with 
apparently  no  less  certainty  than  when  buried  out  of 
eight. 

*3 


354  HOW  CHOPS  GROW. 

Finally,  R.  Hoffmann  (Jaliresbericht  Uber  Agricullur 
Chem.,  1864,  p.  110)  found,  in  special  experiments  with 
24  kinds  of  agricultural  seeds,  that  light  exercises  no 
appreciable  influence  of  any  kind  on  germination. 

The  time  required  for  Germination  varies  exceed- 
ingly according  to  the  kind  of  seed.  It  is  said  that  the 
fresh  seeds  of  the  willow  begin  to  sprout  within  12  hours 
after  falling  to  the  ground.  Those  of  clover,  wheat,  and 
other  grains,  mostly  germinate  in  three  to  -ten  days. 
The  fruits  of  the  walnut,  pine,  and  larch  lie  four  to  six 
weeks  before  sprouting,  while  those  of  some  species  of 
ash,  beech,  and  maple  are  said  not  to  germinate  before 
the  expiration  of  one  and  a  half  or  two  years. 

The  starchy  and  thin-skinned  seeds  quicken  most 
readily.  The  oily  seeds  are  in  general  more  slow,  while 
such  as  are  situated  within  thick  and  horny  or  other- 
wise resistant  envelopes  require  the  longest  periods  to 
excite  growth. 

The  time  necessary  for  germination  depends  naturally 
upon  the  favorableness  of  other  conditions.  Cold  and 
drought  delay  the  process,  when  they  do  not  check  it 
altogether.  Seeds  that  are  buried  deeply  in  the  soil  may 
remain  for  years,  preserving,  but  not  manifesting,  their 
vitality,  because  they  are  either  too  dry,  too  cold,  or 
have  not  sufficient  access  to  oxygen  to  set  the  germ  in 
action. 

Notice  has  already  been  made  of  the  frequent  presence 
in  clover-seed,  for  example,  of  a  small  proportion  of 
seeds  that  have  a  dense  coat  which  prevents  imbibition 
of  water  and  delays  their  germination  for  long  periods. 
See  p.  335. 

To  speak  with  precision,  we  should  distinguish  the 
time  from  planting  the  dry  seed  to  the  commencement 
of  germination,  which  is  marked  by  the  rootlet  becom- 
ing visible,  and  the  period  that  elapses  until  the  process 
is  complete  ;  i.  e.,  until  the  stores  of  the  mother-seed  are 


6EBMINATION.  355 

exhausted,  and  the  young  plant  is  wholly  cast  upon  its 
own  resources. 

At  41°  F.,  in  the  experiments  of  Haberlandt,  the  root- 
let issued  after  four  days,  in  the  case  of  rye,  and  in  five 
to  seven  days  in  that  of  the  other  grains  and  clover. 
The  sugar-beet,  however,  lay  at  this  temperature  22  days 
before  beginning  to  sprout. 

At  51°,  the  time  was  shortened  about  one-half  in  case 
of  the  seeds  just  mentioned.  Maize  required  11,  kidney- 
beans  8,  and  tobacco  31  days  at  this  temperature. 

At  65°  the  cereals,  clover,  peas,  and  flax  began  to 
sprout  in  one  to  two  days ;  maize,  beans,  and  sugar-beet 
in  three  days,  and  tobacco  in  six  days. 

The  time  of  completion  varies  with  the  temperature 
much  more  than  that  of  beginning.  It  is,  for  example, 
according  to  Sachs, 

at  41—55°  for  wheat  and  barley  40—45  days, 
at  95— 100°          "  "        10-12    «• 

At  a  given  temperature  small  seeds  complete  germina- 
tion much  sooner  than  large  ones.  Thus  at  55-60°  the 
process  is  finished 

with  beans  in  30—40  days. 
"      maize  in  30-35      " 
"     wheat  in  2*-25     «• 
"     clover  in   8—10     " 

These  differences  are  simply  due  to  the  fact  that  the 
smaller  seeds  have  smaller  stores  of  nutriment  for  the 
young  plant,  and  are  therefore  more  quickly  exhausted. 

Proper  Depth  of  Sowing. — The  soil  is  usually  the 
medium  of  moisture,  warmth,  etc.,  to  the  seed,  and  it 
affects  germination  only  as  it  influences  the  supply  of 
these  agencies ;  it  is  not  otherwise  essential  to  the  pro- 
cess. The  burying  of  seeds,  when  sown  in  the  field  or 
garden,  serves  to  cover  them  away  from  birds  and  keep 
them  from  drying  up.  In  the  forest,  at  spring-time,  we 
may  see  innumerable  seeds  sprouting  upon  the  surface, 
or  but  half  covered  with  decayed  leaves. 


356  HO^    CfeOPS  GROW. 

While  it  is  the  nearly  universal  result  of  experience  in 
temperate  regions  that  agricultural  seeds  germinate  most 
surely  when  sown  at  a  depth  not  exceeding  one  or  two 
inches,  there  are  circumstances  under  which  a  widely 
different  practice  is  admissible  or  even  essential.  In  the 
light  and  porous  soil  of  the  gardens  of  New  Haven,  peas 
may  be  sown  six  to  eight  inches  deep  without  detriment, 
and  are  thereby  better  secured  from  the  ravages  of  the 
domestic  pigeon. 

The  Moqui  Indians,  dwelling  upon  the  table  lands  of 
the  higher  Colorado,  deposit  the  seeds  of  maize  12  or  14 
inches  below  the  surface.  Thus  sown,  the  plant  thrives, 
while,  if  treated  according  to  the  plan  usual  in  the 
United  States  and  Europe,  it  might  never  appear  above 
ground.  The  reasons  for  such  a  procedure  are  the  fol- 
lowing :  The  country  is  without  rain  and  almost  with- 
out dew.  In  summer  the  sandy  soil  is  continuously 
parched  by  the  sun,  at  a  temperature  often  exceeding 
100°  in  the  shade.  It  is  only  at  the  depth  of  a  foot  or 
more  that  the  seed  finds  the  moisture  needful  for  its 
growth — moisture  furnished  by  the  melting  of  the  winter 
snows.* 

E.  Hoffmann,  experimenting  in  a  light,  loamy  sand, 
upon  24  kinds  of  agricultural  and  market-garden  seeds, 
found  that  all  perished  when  buried  12  inches.  When 
planted  10  inches  deep,  peas,  vetches,  beans,  and  maize, 
alone  came  up ;  at  8  inches  there  appeared,  besides  the 
above,  wheat,  millet,  oats,  barley,  and  colza  ;  at  6  inches, 
those  already  mentioned,  together  with  winter  colza, 
buckwheat,  and  sugar-beets ;  at  4  inches  of  depth  the 
above  and  mustard,  red  and  white  clover,  flax,  horse- 
radish, hemp,  and  turnips ;  finally,  at  3  inches,  lucern 
also  appeared.  Hoffmann  states  that  the  deep-planted 
seeds  generally  sprouted  most  quickly,  and  all  early  dif- 

*  For  these  Interesting  facts,  the  writer  is  indebted  to  Prof.  J.  S. 
Newberry. 


GERMINATION.  357 

ferences  in  development  disappeared  before  the  plants 
blossomed. 

On  the  other  hand,  Grouven,  in  trials  with  sugar-beet 
seed — made,  most  probably,  in  a  well-manured  and  rather 
heavy  soil — found  that  sowing  at  a  depth  of  three-eighths 
to  one  and  a  fourth  inches  gave  the  earliest  and  strongest 
plants ;  seeds  deposited  at  a  depth  of  two  and  a  half 
inches  required  five  days  longer  to  come  up  than  those 
planted  at  three-eighths  of  an  inch.  It  was  further  shown 
that  seeds  sown  shallow,  in  a  fine  wet  clay,  required  four 
to  five  days  longer  to  come  up  than  those  placed  at  the 
same  depth  in  the  ordinary  soil. 

Not  only  the  character  of  the  soil,  which  influences  the 
supply  of  air  and  warmth,  but  the  kind  of  weather 
which  determines  both  temperature  and  degree  of  moist- 
ure, have  their  effect  upon  the  time  of  germination,  and 
since  these  conditions  are  so  variable,  the  rules  of  prac- 
tice are  laid  down,  and  must  be  received,  with  a  certain 
latitude. 

§4. 

THE  CHEMICAL  PHYSIOLOGY  OP  GERMINATION. 

• 

THE  NUTRITION  OF  THE  SEEDLING. — The  young 
plant  grows  at  first  exclusively  at  the  expense  of  the 
seed.  It  may  be  aptly  compared  to  the  suckling  animal, 
which,  when  new-born,  is  incapable  of  providing  its 
own  nourishment,  but  depends  upon  the  milk  of  its 
mother. 

The  Nutrition  of  the  Seedling  falls  into  three  pro- 
cesses, which,  though  distinct  in  character,  proceed  sim- 
ultaneously. These  are  :  1,  Solution  of  the  Nutritive 
Matters  of  the  Cotyledons  or  Endosperm  ;  2,  Transfer ; 
and  3,  Assimilation  of  the  same. 

1.  The  Act  of  Solution  has  no  difficulty  JL  case  of 


358  HOW  CROPS  GROW. 

dextrin,  gum,  the  sugars,  and  soluble  proteids.  The 
water  which  the  seed  imbibes,  to  the  extent  of  one-fourth 
to  five-fourths  of  its  weight,  at  once  dissolves  them. 

It  is  otherwise  with  the  fats  or  oils,  with  starch  and 
with  proteids,  which,  as  such,  are  nearly  or  altogether 
insoluble  in  water.  In  the  act  of  germination  provision 
is  made  for  transforming  these  bodies  into  the  soluble 
ones  above  mentioned.  So  far  as  these  changes  have 
been  traced,  they  are  as  follows  : 

Solution  of  Fats. — Sachs  was  the  first  to  show  that 
squash-seeds,  which,  when  ripe,  contain  no  starch, 
sugar,  or  dextrin,  but  are  very  rich  in  oil  (50%)  and 
albuminoids  (40%),  suffer  by  germination  such  chemical 
change  that  the  oil  rapidly  diminishes  in  quantity  (nine- 
tenths  disappear),  while,  at  the  same  time,  starch,  and 
in  some  cases  sugar,  is  formed.  (Vs.  St.,  Ill,  p.  ].) 

Solution  of  Starch. — The  starch  that  is  thus  organized 
from  the  fat  of  the  oily  seeds,  or  that  which  exists 
ready-formed  in  the  farinaceous  (floury)  seeds,  undergoes 
further  changes,  which  have  been  previously  alluded  to 
(p.  50),  whereby  it  is  converted  into  substances  that  are 
soluble  in  water,  viz.,  dextrin  and  dextrose. 

Solution  of  Albuminoids. — Finally,  the  insoluble  al- 
buminoids are  gradually  transformed  into  soluble  modi- 
fications. 

Chemistry  of  Malt. — The  preparation  and  proper- 
ties of  malt  may  serve  to  give  an  insight  into  the  nature 
of  the  chemical  metamorphoses  that  have  just  been 
indicated. 

The  preparation  is  in  this  wise.  Barley  or  wheat 
(sometimes  rye)  is  soaked  in  water  until  the  kernels  are 
soft  to  the  fingers ;  then  it  is  drained  and  thrown  up  in 
heaps.  The  masses  of  soaked  grain  shortly  dry,  become 
heated,  and  in  a  few  days  the  embryos  send  forth  their 
radicles.  The  heaps  are  shoveled  over,  and  spread  out 
so  as  to  avoid  too  great  a  rise  of  temperature,  and  when 


GERMINATION.  359 

the  sprouts  are  about  half  an  inch  in  length,  the  germin- 
ation is  checked  by  drying.  The  dry  mass,  after  remov- 
ing the  sprouts  (radicles),  is  malt,  such  as  is  used  in  the 
manufacture  of  beer. 

Malt  thus  consists  of  starchy  seeds,  whose  germination 
has  been  checked  while  in  its  early  stages.  The  only 
product  of  the  beginning  growth — the  sprouts — being 
removed,  it  exhibits  in  the  residual  seed  the  first  results 
of  the  process  of  solution. 

The  following  figures,  derived  from  the  researches  of 
Stein,  in  Dresden  ( Wilda's  Centralblatt,  1860,  2,  pp.  8- 
23),  exhibit  the  composition  of  100  parts  of  Barley,  and 
of  the  92  parts  of  Malt,  and  the  two  and  a  half  of  Sprouts 
which  100  parts  of  Barley  yield.* 

,  „,  100  pts.  of )  _  ( 92  pts.  of )   ,   (     2J  of     >  , 

Composition  of  Barley.    |  =  {     >Ialt.     j  +  { Sprouts. }  + 

Ash, 2.42  2.11  0.29 

Starch, 54.48  47.43 

Fat, 3.56  2.09  0.08 

tasoluble   Albuminoids, 11.02  9.02  0.37 

Soluble  Albuminoids 1.26  1.96  0.40 

Dextrin, t 6.50  6.951 

Extractive  Matters  (soluble  in  0.47 

water  and  destitute  of  nitrogen)  0.90  3.68  ) 

Cellulose, 19.86  18.76  0.89 


100.  92.  2.5 

It  is  seen  from  the  above  statement  that  starch,  fat, 
and  insoluble  albuminoids  have  diminished  in  the  malt- 
ing process  ;  while  soluble  albuminoids,  dextrin,  and 
other  soluble  non-nitrogenous  matters  have  somewhat 
increased  in  quantity.  "With  exception  of  3%  of  soluble 
"extractive  matters,"  \  the  differences  in  composition 
between  barley  and  malt  are  not  striking. 

«  The  analyses  refer  to  the  materials  in  the  dry  state.  Ordinarily 
they  contain  from  10  to  16  per  cent  of  water.  It  must  not  be  omitted  to 
mention  that  the  proportions  of  malt  and  sprouts,  as  well  as  their 
composition,  vary  somewhat  according  to  circumstances  ;  and  further- 
more, the  best  analyses  which  it  is  possible  to  make  are  but  approxi- 
mate. 

t  Later  investigators  deny  the  existence  of  dextrin  in  barley,  but 
find,  instead,  amidulin  and  amylan.  See  p.  62,  note. 

t  The  term  extractive  matters  is  here  applied  to  soluble  substances, 
whose  precise  nature  is  not  understood.  They  constitute  a  mixture 
which  the  chemist  to  not  able  to  analyze. 


360  OW  CROPS  GROW. 


The  properties  of  the  two  are,  however,  remarkably 
different.  If  malt  be  pulverized  and  stirred  in  warm 
water  (155°  F.)  for  an  hour  or  two,  the  whole  of  the 
starch  disappears,  while  sugar  and  dextrin  take  its  place. 
The  former  is  recognized  by  the  sweet  taste  of  the  wort. 
as  the  solution  is  called.  On  heating  the  wort  to  boiling, 
a  little  albuminoid  is  coagulated,  and  may  be  separ- 
ated by  filtering.  This  comes  in  part  from  the  trans- 
formation of  the  insoluble  albuminoids  of  the  barley. 
On  adding  to  the  filtered  liquid  its  own  bulk  of  alcohol, 
dextrin  becomes  evident,  being  precipitated  as  a  white 
powder. 

Furthermore,  if  we  mix  two  to  three  parts  of  starch 
with  one  of  malt,  we  find  that  the  whole  undergoes  the 
same  change.  An  additional  quantity  of  starch  remains 
unaltered. 

The  process  of  germination  thus  develops  in  the  seed 
an  agency  by  which  the  conversion  of  starch  into  soluble 
carbhydrates  is  accomplished  with  great  rapidity. 

Diastase  —  Payen  &  Persoz  attributed  this  action  to 
the  nitrogenous  ferment  which  they  termed  Diastase, 
and  which  is  found  in  the  germinating  seed  in  the  vicin- 
ity of  the  embryo,  but  not  in  the  radicles.  They  assert 
that  one  part  of  diastase  is  capable  of  transforming  2,000 
parts  of  starch,  first  into  dextrin  and  finally  into  sugar, 
and  that  malt  yields  one  five-hundredth  of  its  weight  of 
this  substance.  See  p.  103. 

A  short  time  previous  to  the  investigations  of  Payen 
&  Persoz  (1833),  Saussure  found  that  Muceclin,*  the 
soluble  nitrogenous  body  which  may  be  extracted  from 
gluten  (p.  92,  note),  transforms  starch-  in  the  manner 
above  described,  and  it  is  now  known  that  various  albu- 
minoids may  produce  the  same  effect,  although  the  rap- 


*  Saussure  designated  this  body  mncln,  but  this  term  being  established 
as  the  name  of  the  characteristic  ingredient  of  animal  mucus,  Kitthau- 
sea  has  replaced  it  by  mucedin. 


GERMINATION. 


361 


idity  of  the  action  and  the  amount  of  effect  are  usually 
far  less  than  that  exhibited  by  the  so-called  diastase. 

It  must  not  be  forgotten,  however,  that  in  all  cases  in 
which  the  conversion  of  starch  into  dextrin  and  sugar  ia 
accomplished  artificially,  an  elevated  temperature  is  re- 
quired, whereas,  in  the  natural  process,  as  shown  in  the 
germinating  seed,  the  change  goes  on  at  ordinary  or  even 
low  temperatures. 

It  is  generally  taught  that  oxygen,  acting  on  the  albu- 
minoids in  presence  of  water,  and  within  a  certain  range 
of  temperature,  induces  the  decomposition  which  confers 
on  them  the  power  in  question. 

The  necessity  for  oxygen  in  the  act  of  germination  has 
been  thus  accounted  for,  as  needful  to  the  solution  of 
the  starch,  etc.,  of  the  cotyledons. 

This  may  be  true  at  first,  but,  as  we  shall  presently  see, 
the  chief  action  of  oxygen  is  probably  of  another  kind. 

How  diastase  or  other  similar  substances  accomplish 
the  change  in  question  is  not  certainly  known. 

Soluble  Starch. — The  conversion  of  starch  into 
sugar  and  dextrin  is  thus  in  a  sense  explained.  This  is 

not,  however,  the  only  change 
of  which  starch  is  suscepti- 
ble. In  the  bean  (Phaseol- 
us  multiflorus)  Sachs  (Sitz- 
ungsberichte  der  Wiener 
Akad.,  XXXVII,  57)  in- 
forms us  that  the  starch  of 
the  cotyledons  is  dissolved, 
passes  into  the  seedling,  and 
reappears  (in  part,  at  least) 
as  starch,  without  conver- 
sion into  dextrin  or  sugar, 
as  these  substances  do  not  appear  in  the  cotyledons  during 
any  period  of  germination,  except  in  small  quantity  near 
$e  joining  of  #M?  seedling,  Compare  p,  §3, 


Fig.  65. 


362  HOW  CROPS  GROW. 

The  same  authority  gives  the  following  account  of  the 
microscopic  changes  observed  in  the  starch-grains  them- 
selves, as  they  undergo  solution.  The  starch-grains  of 
the  bean  have  a  narrow  interior  cavity  (as  seen  in  Fig. 
65,  1).  This  at  first  becomes  filled  with  a  liquid. 
Next,  the  cavity  appears  enlarged  (2),  its  borders  assume 
a  corroded  appearance  (3,  4),  and  frequently  channels 
are  seen  extending  to  the  surface  (4,  5,  6).  Finally,  the 
cavity  becomes  so  large,  and  the  channels  so  extended, 
that  the  starch-grain  falls  to  pieces  (7,  8).  Solution 
continues  on  the  fragments  until  they  have  completely 
disappeared. 

Soluble  Albuminoids. — The  insoluble  proteids  of 
the  seed  are  gradually  transferred  to  the  young  plant, 
probably  by  ferment-actions  similar  to  those  referred 
to  under  the  heading  "  Proteoses  and  Peptones,"  p.  100. 

The  production  of  small  quantities  of  acetic  and  lactic 
acids  (the  acids  of  vinegar  and  of  sour  milk)  has  been 
observed  in  germination.  These  acids  perhaps  assist  in 
the  solution  of  the  albuminoids. 

Gaseous  Products  of  Germination. — Before  leav- 
ing this  part  of  our  subject,  it  is  proper  to  notice  some 
other  results  of  germination  which  have  been  thought  to 
belong  to  the  process  of  solution.  On  referring  to  the 
table  of  the  composition  of  malt,  we  find  that  100  parts 
of  dry  barley  yield  92  parts  of  malt  and  2%  of  sprouts, 
leaving  5£  parts  unaccounted  for.  In  the  malting  pro- 
cess, 1£  parts  of  the  grain  are  dissolved  in  the  water  in 
which  it  is  soaked.  The  remaining  4  parts  escape  into 
the  atmosphere  in  the  gaseous  form. 

Of  the  elements  that  assume  the  gaseous  condition, 
carbon  does  so  to  the  greatest  extent.  It  unites  with 
atmospheric  oxygen  (partly  with  the  oxygen  of  the 
seed,  according  to  Oudemans),  producing  carbonic  acid 
gas  (C02).  Hydrogen  is  likewise  separated,  partly  in 
union  with  oxygen,  as  water  (H?0),  but  to  some  degree 


GERMINATION.  363 

in  the  free  state.  Free  nitrogen  appears  in  considerable 
amount  (Schulz,  Jour,  far  Prakt.  Chem.,  87,  p.  163), 
while  very  minute  quantities  of  Hydrogen  and  of  Nitro- 
gen combine  to  gaseous  ammonia  (NH3). 

Heat  developed  in  Germination. — These  chemical 
changes,  like  all  processes  of  oxidation,  are  accompanied 
with  the  production  of  heat.  The  elevation  of  temper- 
ature may  be  imperceptible  in  the  germination  of  a  sin- 
gle seed,  but  the  heaps  of  sprouting  grain  seen  in  the 
malt-house,  warm  so  rapidly  and  to  such  an  extent  that 
much  care  is  requisite  to  regulate  the  process  ;  otherwise 
the  malt  is  damaged  by  over-heating. 

2.  The  Transfer  of  the  Nutriment  of  the  Seed- 
ling from  the  cotyledons  or  endosperm  where  it  has  un- 
dergone solution,  takes  place  through  the  medium  of  the 
water  which  the  seed  absorbs  so  largely  at  first.  This 
water  fills  the  cells  of  the  seed,  and,  dissolving  their  con- 
tents, carries  them  into  the  young  plant  as  rapidly  as 
they  are  required.  The  path  of  their  transfer  lies  through 
the  point  where  the  embryo  is  attached  to  the  cotyle- 
dons ;  thence  they  are  distributed  at  first  chiefly  down- 
wards into  the  extending  radicles,  after  a  little  while 
both  downwards  and  upwards  toward  the  extremities  of 
the  seedling. 

Sachs  has  observed  that  the  carbhydrates  (sugar  and 
dextrin)  occupy  the  cellular  tissue  of  the  rind  and  pith, 
which  are  penetrated  by  numerous  air-passages ;  while 
at  first  the  albuminoids  chiefly  diffuse  themselves  through 
the  intermediate  cambial  tissue,  which  is  destitute  oi 
air-passages,  and  are  present  in  largest  relative  quantity 
at  the  extreme  ends  of  the  rootlets  and  of  the  plumule. 

In  another  chapter  we  shall  notice  at  length  the  phe- 
nomena and  physical  laws  which  govern  the  diffusion  oi 
liquids  into  each  other  and  through  membranes  similar 
to  those  which  constitute  the  walls  of  the  cells  of  plants, 
and  there  shall  be  able  to  gather  some  idea  of  the  causes 


364  HOW  CEOPS  QBOW. 

which  set  up  and  maintain  the  transfer  of  the  materials 
of  the  seed  into  the  infant  plant. 

,3.  Assimilation  is  the  conversion  of  the  transferred 
nutriment  into  the  substance  of  the  plant  itself.  This 
process  involves  two  stages,  the  first  being  a  chemical, 
the  second,  a  structural  transformation. 

The  chemical  changes  in  the  embryo  are,  in  part, 
simply  the  reverse  of  those  which  occur  in  the  cotyle- 
dons; viz.,  the  soluble  and  structureless  proximate  prin- 
ciples are  metamorphosed  into  the  insoluble  and  organ- 
ized ones  of  the  same  or  similar  chemical  composition. 
Thus,  dextrin  may  pass  into  cellulose,  and  the  soluble 
albuminoids  may  revert  in  part  to  the  insoluble  condi- 
tion in  which  they  existed  in  the  ripe  seed. 

But  many  other  and  more  intricate  ehanges  proceed  in 
the  act  of  assimilation.  With  regard  to  a  few  of  these 
we  have  some  imperfect  knowledge. 

Dr.  Sachs  informs  us  that  when  the  embryo  begins  to 
grow,  its  expansion  at  first  consists  in  the  enlargement 
of  the  ready-formed  cells.  As  a  part  elongates,  the 
starch  which  it  contains  (or  which  is  formed  in  the  early 
stages  of  this  extension)  disappears,  and  sugar  is  found 
in  its  stead,  dissolved  in  the  juices  of  the  cells.  When 
the  organ  has  attained  its  full  size,  sugar  can  no  longer 
be  detected ;  while  the  walls  of  the  cells  are  found  to 
have  grown  both  in  circumference  and  thickness,  thus 
indicating  the  accumulation  of  cellulose. 

Oxygen  Gas  needful  to  Assimilation. — Traube 
has  made  some  experiments,  which  prove  conclusively 
that  the  process  of  assimilation  requires  free  oxygen  to 
surround  and  to  be  absorbed  by  the  growing  parts  of  the 
germ.  This  observer  found  that  newly-sprouted  pea- 
seedlings  continued  to  develop  in  a  normal  manner  when 
the  cotyledons,  radicles,  and  lower  part  of  the  stem 
were  withdrawn  from  the  influence  of  oxygen  by  coat- 
ing with  varnish  or  oil.  On  the  other  hand,  when  the 


GERMINATION.  365 

tip  of  the  plumule,  for  the  length  of  about  an  inch,  was 
coated  with  oil  thickened  with  chalk,  or  when  by  any 
means  this  part  of  the  plant  was  withdrawn  from  contact 
with  free  oxygen,  the  seedling  ceased  to  grow,  withered, 
and  shortly  perished.  Traube  observed  the  elongation 
of  the  stem  by  the  following  expedient. 

A  young  pea-plant  was  fastened  by  the  cotyledons  to  a 
rod,  and  the  stem  and  rod  were  both  graduated  by  deli- 
cate cross-lines,  laid  on  at  equal  intervals,  by  means  of  a 
brush  dipped  in  a  mixture  of  oil  and  indigo.  The 
growth  of  the  stem  was  now  manifest  by  the  widening  of 
the  spaces  between  the  lines ;  and,  by  comparison  with 
those  on  the  rod,  Traube  remarked  that  no  growth  took 
place  at  a  distance  of  more  than  ten  to  twelve  lines  from 
the  base  of  the  terminal  bud. 

Here,  then,  is  a  coincidence  which  appears  to  demon- 
strate that  free  oxygen  must  have  access  to  a  growing 
part.  The  fact  is  further  shown  by  varnishing  one  side 
of  the  stem  of  a  young  pea.  The  varnished  side  ceases 
to  extend,  the  uncoated  portion  continues  enlarging, 
which  results  in  a  curvature  of  the  stem. 

Traube  further  indicates  in  what  manner  the  elabora- 
tion of  cellulose  from  sugar  may  require  the  co-operation 
of  oxygen  and  evolution  of  carbon  dioxide,  as  expressed 
by  the  subjoined  equation. 

Glucose.       Oxygen.    Carbon  dioxide.    Water.          Cellulose. 
2(C12H14012)    +    240      =      12    (CO,)     +     14  (H,O)    +    C^H^d,,. 

When  the  act  of  germination  is  finished,  which  occurs 
as  soon  as  the  cotyledons  and  endosperm  are  exhausted 
of  all  their  soluble  matters,  the  plant  begins  a  fully  inde- 
pendent life.  Previously,  however,  to  being  thus  thrown 
upon  its  own  resources,  it  has  developed  all  the  organs 
needful  to  collect  its  food  from  without ;  it  has  unfolded 
its  perfect  leaves  into  the  atmosphere,  and  pervaded  9 
portion  of  soil  with  its  rootlets. 


366  HOW  CROPS  GROW. 

During  the  latter  stages  of  germination  it  gathers  its 
nutriment  both  from  the  parent  seed  and  from  the  exter- 
nal sources  which  afterward  serve  exclusively  for  its 
support. 

Being  fully  provided  with  the  apparatus  of  nutrition, 
its  development  suffers  no  check  from  the  exhaustion  of 
the  mother  seed,  unless  it  has  germinated  in  a  sterile 
soil,  or  under  other  conditions  adverse  to  vegetative  life. 


CHAPTER   II. 
§1. 

THE  FOOD  OF  THE  PLANT  WHEN"  INDEPENDENT  OF  THE 

SEED. 

This  subject  will  be  sketched  in  this  place  in  but  the 
briefest  outlines.  To  present  it  fully  would  necessitate 
entering  into  a  detailed  consideration  of  the  Atmosphere 
and  of  the  Soil,  whose  relations  to  the  Plant,  those  of  the 
soil  especially,  are  very  numerous  and  complicated.  A 
separate  volume  is  therefore  required  for  the  adequate 
treatment  of  these  topics. 

The  Roots  of  a  plant,  which  are  in  intimate  contact 
with  the  soil,  absorb  thence  the  water  that  fills  the  active 
cells  ;  they  also  imbibe  such  salts  as  the  water  of  the  soil 
holds  in  solution  ;  they  likewise  act  directly  on  the  soil, 
and  dissolve  substances,  which  are  thus  first  made  of 
avail  to  them.  The  compounds  that  the  plant  must 
derive  from  the  soil  are  those  which  are  found  in  its  ash, 
since  these  are  not  volatile,  and  cannot,  therefore,  exist 
in  the  atmosphere.  The  root,  however,  commonly  takes 


FOOD  AFTER    GERMINATION.  367 

up  some  other  elements  of  its  nutrition  to  which  it  has 
immediate  access.  Leaving  out  of  view,  for  the  present, 
those  matters  which,  though  found  in  the  plant,  appear 
to  be  unessential  to  its  growth,  viz.,  silica  and  sodium 
salts,  the  roots  absorb  the  following  substances,  viz.  : 


Sulphates  "I               f  Potassium, 

Phosphates  ,      |  Calcium, 

Nitrates  and  f  Magnesium  and 

Chlorides  _  Iron. 


These  salts  enter  the  plant  by  the  absorbent  surfaces 
of  the  younger  rootlets,  and  pass  upwards,  through  the 
stem,  to  the  leaves  and  to  the  new-forming  buds. 

The  Leaves,  which  are  unfolded  to  the  air,  gather 
from  it  Carbon  dioxide  Gas.  This  compound  suffers 
decomposition  in  the  plant ;  its  Carbon  remains  there, 
its  Oxygen  or  an  equivalent  quantity,  very  nearly,  is 
thrown  off  into  the  air  again. 

The  decomposition  of  carbon  dioxide  takes  place  only 
by  day  and  under  the  influence  of  the  sun's  light. 

From  the  carbon  thus  acquired  and  the  elements  of 
water  with  the  co-operation  of  the  ash-ingredients,  the 
plant  organizes  the  Carbhydrates.  Probably  some  of  the 
glucoses  are  the  first  products  of  this  synthesis.  Starch, 
in  the  form  of  granules,  is  the  first  product  that  is 
recognizable  by  help  of  the  microscope. 

The  formation  of  carbhydrates  appears  to  proceed  in 
the  chlorophyl-cells  of  the  leaf,  where  starch-granules 
first  make  their  appearance. 

The  Albuminoids  require  for  their  production  the 
presence  of  a  compound  of  Nitrogen.  The  salts  of 
Nitric  Acid  (nitrates)  are  commonly  the  chief,  and  may 
be  the  only,  supply  of  this  element. ' 

The  other  proximate  principles,  the  fats,  the  alkaloids, 
and  the  acids,  are  built  up  from  the  same  food-elements. 
In  most  cases  the  steps  in  the  construction  of  organic 
matters  are  unknown  to  us,  or  subjects  of  uncertain  con- 
jecture. 


HOW  CHOPS  GEOW. 

The  carbhydrates,  albuminoids,  etc.,  that  are  organ- 
ized  in  the  foliage,  are  not  only  transformed  into  the 
solid  tissues  of  the  leaf,  but  descend  and  diffuse  to  every 
active  organ  of  the  plant. 

The  plant  has,  within  certain  limits,  a  power  of  select- 
ting  its  food.  The  sea- weed,  as  has  been  remarked, 
contains  more  potash  than  soda,  altbough  the  latter  is 
30  times  more  abundant  than  the  former  in  the  water  of 
the  ocean.  Vegetation  cannot,  however,  entirely  shut 
out  either  excess  of  nutritive  matters  or  bodies  that  are 
of  no  use  or  even  poisonous  to  it. 

The  functions  of  the  Atmosphere  are  essentially  the 
same  towards  plants,  whether  growing  under  the  con- 
ditions of  water-culture  or  under  those  of  agriculture. 

The  Soil,  on  the  other  hand,  has  offices  which  are  pe- 
culiar to  itself.  We  have  seen  that  the  roots  of  a  plant 
have  the  power  to  decompose  salts,  e.  g.,  potassium 
nitrate  and  ammonium  chloride  (p.  184),  in  order  to 
appropriate  one  of  their  ingredients,  the  other  being 
rejected.  In  water-culture,  the  experimenter  must  have 
a  care  to  remove  the  substance  which  would  thus  accu- 
mulate to  the  detriment  of  the  plant.  In  agriculture, 
the  soil,  by  virtue  of  its  chemical  and  physical  qualities, 
commonly  renders  such  rejected  matters  comparatively 
insoluble,  and  therefore  innocuous. 

The  Atmosphere  is  nearly  invariable  in  its  composi- 
tion at  all  times  and  over  all  parts  of  the  earth's  surface. 
Its  power  of  directly  feeding  crops  has,  therefore,  a  nat- 
ural limit,  which  cannot  be  increased  by  art. 

The  Soil,  on  the  other  hand,  is  very  variable  in  com- 
position and  quality,  and  may  be  enriched  and  improved, 
or  deteriorated  and  exhausted. 

From  the  Atmosphere  the  crop  can  derive  no  appreci- 
able quantity  of  those  elements  that  are  found  in  its 
Ash. 

In  the  Soil,  however,  from  the  waste  of  both  plants 


MOTION  OP  THE    JUICES.  369 

animals,  may  accumulate  large  supplies  of  all  the 
elements  of  the  Volatile  part  of  Plants.  Carbon,  cer- 
tainly in  the  form  of  carbon  dioxide,  probably  or  possi- 
bly in  the  condition  of  Humus  (Vegetable  Mold;  Swamp 
Muck),  may  thus  be  put  as  food,  at  the  disposition 
of  the  plant.  Nitrogen  is  chiefly  furnished  to  crops  by 
the  soil.  Nitrates  are  formed  in  the  latter  from  various 
sources,  and  ammonia-salts,  together  with  certain  proxi- 
mate animal  principles,  viz.,  urea,  guanin,  tyrosin,  uric 
acid  and  hippuric  acid,  likewise  serve  to  supply  nitrogen 
to  vegetation  and  are  often  ingredients  of  the  best  ma- 
nures. It  is,  too,  from  the  soil  that  the  crop  gathers  all 
the  Water  it  requires,  which  not  only  serves  as  the  fluid 
medium  of  its  chemical  and  structural  metamorphoses, 
but  likewise  must  be  regarded  as  the  material  from  which 
it  mostly  appropriates  the  Hydrogen  and  Oxygen  of  its 
solid  components. 

§*• 

THE      JUICES    OF    THE    PLANT,     THEIB    NATUBE     AND 
MOVEMENTS. 

Very  erroneous  notions  have  been  entertained  with 
regard  to  the  nature  and  motion  of  sap.  It  was  formerly 
taught  that  there  are  two  regular  and  opposite  currents 
of  sap  circulating  in  the  plant.  It  was  stated  that  the 
"crude  sap"  is  taken  up  from  the  soil  by  the  roots, 
ascends  through  the  vessels  (ducts)  of  the  wood,  to  the 
leaves,  there  is  concentrated  by  evaporation,  "elabor- 
ated" by  the  processes  that  go  on  in  the  foliage,  and 
thence  descends  through  the  vessels  of  the  inner  bark, 
nourishing  these  tissues  in  its  way  down.  The  facts 
from  which  this  theory  of  the  sap  naturally  arose  admit 
of  a  very  different  interpretation ;  while  numerous  con- 
24 


370  HOW  CEOPS  GROW. 

eiderations  demonstrate  the  essential  falsity  of  the  theory 
itself. 

Flow  of  Sap  in  the  Plant — not  Constant  or 
Necessary. — We  speak  of  the  Flow  of  Sap  as  if  a  rapid 
current  were  incessantly  streaming  through  the  plant, 
as  the  blood  circulates  in  the  arteries  and  veins  cf  an  ani- 
mal. This  is  an  erroneous  conception. 

A  maple  in  early  March,  without  foliage,  with  its 
whole  stem  enveloped  in  a  nearly  impervious  bark,  its 
buds  wrapped  up  in  horny  scales,  and  its  roots  sur- 
rounded by  cold  or  frozen  soil,  cannot  be  supposed  to  have 
its  sap  in  motion.  Its  juices  must  be  nearly  or  abso- 
lutely at  rest,  and  when  sap  runs  copiously  from  an  ori- 
fice made  in  the  trunk,  it  is  simply  because  the  tissues 
are  charged  with  water  under  pressure,  which  escapes  at 
any  outlet  that  may  be  opened  for  it.  The  sap  is  at  rest 
until  motion  is  caused  by  a  perforation  of  the  bark  and 
new  wood.  So,  too,  when  a  plant  in  early  leaf  is  situa- 
ted in  an  atmosphere  charged  with  moisture,  as  happens 
on  a  rainy  day,  there  is  little  motion  of  its  sap,  although, 
if  wounded,  motion  may  be  established,  and  water  may 
stream  more  or  less  from  all  parts  of  the  plant  towards 
the  cut. 

Sap  does  move  in  the  plant  when  evaporation  of  water 
goes  on  from  the  surface  of  the  foliage.  This  always 
happens  whenever  the  air  is  not  saturated  with  vapor. 
When  a  wet  cloth  hung  out,  dries  rapidly  by  giving  up 
its  moisture  to  the  air,  then  the  leaves  of  plants  lose 
their  water  more  or  less  readily,  according  to  the  nature 
of  the  foliage. 

Mr.  Lawes  found  that  in  the  moist  climate  of  England 
common  plants  (Wheat,  Barley,  Beans,  Peas,  and  Clover) 
exhaled,  during  five  months  of  growth,  more  than  200 
times  their  (dry)  weight  of  water.  Hellriegel,  in  the 
drier  climate  of  Dahme,  Prussia,  observed  exhalation  to 
average  300  times  the  dry  weight  of  various  common 


MOTION  OF  THE   JUICES.  371 

crops  (p.  312).  The  water  that  thus  evaporates  from  the 
leaves  is  supplied  by  the  soil,  and,  entering  the  roots, 
more  or  less  rapidly  streams  upwards  through  the  stem  as 
long  as  a  waste  is  to  be  supplied,  but  this  flow  ceases 
when  evaporation  from  the  foliage  is  suppressed. 

The  upward  motion  of  sap  is  therefore  to  a  great  de- 
great  independent  of  the  vital  processes,  and  compara- 
tively unessential  to  the  welfare  of  the  plant. 

Flow  of  Sap  from  the  Plant ;  "  Bleeding."— It 
is  a  familiar  fact,  that  from  a  maple  tree  "  tapped  "  in 
spring-time,  or  from  a  grape-vine  wounded  at  the  same 
season,  a  copious  flow  of  sap  takes  place,  which  continues 
for  a  number  of  weeks.  The  escape  of  liquid  from  the 
vine  is  commonly  termed  "  bleeding,"  and  while  this 
rapid  issue  of  sap  is  thus  strikingly  exhibited  in  compar- 
atively few  cases,  bleeding  appears  to  be  a  universal  phe- 
nomenon, one  that  may  occur,  at  least,  to  some  degree, 
under  certain  conditions  with  very  many  plants. 

The  conditions  under  which  sap  flows  are  various, 
according  to  the  character  of  the  plant.  Our  perennial 
trees  have  their  annual  period  of  active  growth  in  the 
warm  season,  and  their  vegetative  functions  are  nearly 
suppressed  during  cold  weather.  As  spring  approaches 
the  tree  renews  its  growth,  and  the  first  evidence  of 
change  within  is  furnished  by  its  bleeding  when  an  open- 
ing is  made  through  the  bark  into  the  young  wood.  A 
maple,  tapped  for  making  sugar,  loses  nothing  until  the 
spring  warmth  attains  a  certain  intensity,  and  then  sap 
begins  to  flow  from  the  wounds  in  its  trunk.  The  flow 
is  not  constant,  but  fluctuates  with  the  thermometer, 
being  more  copious  when  the  weather  is  warm,  and  fall- 
ing off  or  suffering  check  altogether  as  it  is  colder. 

The  stem  of  the  living  maple  is  always  charged  with 
water,  and  never  more  so  than  in  winter.*  This  water 

*  Experiments  made  In  Tharand,  Saxony,  under  direction  of  Stoeck- 
hardt,  show  that  the  proportion  of  water,  both  in  the  bark  and  wood 


372  HOW  CROPS  GROW. 

is  either  pumped  into  the  plant,  so  to  speak,  "by  the  root- 
power  already  noticed  (p.  269),  or  it  is  generated  in 
the  trunk  itself.  The  water  contained  in  the  stem  in 
winter  is  undoubtedly  that  raised  from  the  soil  in  the 
autumn.  That  which  first  flows  from  an  auger-hole,  in 
March,  may  be  simply  what  was  thus  stored  in  the  trunk  ; 
but,  as  the  escape  of  sap  goes  on  for  14  to  20  days  at  the 
rate  of  several  gallons  per  day  from  a  single  tree,  new 
quantities  of  water  must  be  continually  supplied.  That 
these  are  pumped  in  from  the  root  is,  at  first  thought, 
difficult  to  understand,  because,  as  we  have  seen  (p.  272), 
the  root-power  is  suspended  by  a  certain  low  tempera- 
ture (unknown  in  case  of  the  maple),  and  the  flow  of 
eap  often  begins  when  the  ground  is  covered  with  one  or 
two  feet  of  snow,  and  when  we  cannot  suppose  the  soil 
to  have  a  higher  temperature  than  it  had  during  the  pre- 
vious winter  months.  Nevertheless,  it  must  be  that  the 
deeper  roots  are  warm  enough  to  be  active  all  the  winter 
through,  and  that  they  begin  their  action  as  soon  as  the 
trunk  acquires  a  temperature  sufficiently  high  to  admit 
the  movement  of  water  in  it.  That  water  may  be  pro- 
duced in  the  trunk  itself  to  a  slight  extent  is  by  no 
means  impossible,  for  chemical  changes  go  on  there  in 
spring-time  with  much  rapidity,  whereby  the  sugar  of 
the  sap  is  formed.  These  changes  have  not  been  suffi- 
ciently investigated,  however,  to  prove  or  disprove  the 
generation  of  water,  and  we  must,  in  any  case,  assume 
that  it  is  the  root-power  which  chiefly  maintains  a  pres- 
sure of  liquid  in  the  tree. 

The  issue  of  sap  from  the  maple  tree  in  the  sugar- 
season  is  closely  connected  with  the  changes  of  tempera- 
ture that  take  place  above  ground.  The  sap  begins  to 

of  trees,  varies  considerably  in  different  seasons  of  the  year,  ranging, 
in  case  of  the  beech,  from  35  to  49  per  cent  of  the  fresh-felled  tree.  The 
greatest  proportion  of  water  in  the  wood  was  found  in  the  months  of 
December  and  January ;  in  the  bark,  in  March  to  May.  The  minimum 
of  water  in  the  wood  occurred  in  May,  June,  and  July;  in  the  bark, 
much  irregularity  was  observed.  Chem.  Ackersmann,  1866,  p.  159. 


MOTION  OF  THE    JUICES.  373 

flow  from  a  cut  when  the  trunk  itself  is  warmed  to  a  cer- 
tain point  and,  in  general,  the  flow  appears  to  be  the 
more  rapid  the  warmer  the  trunk.  During  warm,  clear 
days,  the  radiant  heat  of  the  sun  is  absorbed  by  the  dark, 
rough  surface  of  the  tree  most  abundantly ;  then  the 
'jemperature  of  the  latter  rises  most  speedily  and  acquires 
the  greatest  elevation — even  surpasses  that  of  the  atmos- 
phere by  several  degrees  ;  then,  too,  the  yield  of  sap  is 
most  copious.  On  clear  nights,  cooling  of  the  tree  takes 
place  with  corresponding  rapidity  ;  then  the  snow  or 
surface  of  the  ground  is  frozen,  and  the  flow  of  sap  is 
checked  altogether.  From  trees  that  have  a  sunny  ex- 
posure, sap  runs  earlier  and  faster  than  from  those  hav- 
ing a  cold  northern  aspect.  Sap  starts  sooner  from  the 
spiles  on  the  south  side  of  a  tree  than  from  those  towards 
the  north. 

Dnchartre  (Comptes  Rendus,  IX,  754)  passed  a  vine 
situated  in  a  grapery,  out  of  doors,  and  back  again, 
through  holes,  so  that  a  middle  portion  of  the  stem  was 
exposed  to  a  steady  winter  temperature  ranging  from  18° 
to  10°  F.,  while  the  remainder  of  the  vine,  in  the  house, 
was  surrounded  by  an  atmosphere  of  70°  F.  Under 
these  circumstances  the  buds  within  developed  vigor- 
ously, but  those  without  remained  dormant  and  opened 
not  a  day  sooner  than  buds  upon  an  adjacent  vine  whose 
stem  was  all  out  of  doors.  That  sap  passed  through  the 
cold  part  of  the  stem  was  shown  by  the  fact  that  the 
interior  shoots  sometimes  wilted,  but  again  recovered 
their  turgor,  which  could  only  happen  from  the  partial 
suppression  and  renewal  of  a  supply  of  water  through  the 
stem.  Payen  examined  the  wood  of  the  vine  at  the  con- 
clusion of  the  experiment,  and  found  the  starch  which  it 
originally  contained  to  have  been  equally  removed  from 
the  warm  and  the  exposed  parts. 

That  the  rate  at  which  sap  passed  through  the  stem 
was  influenced  by  its  temperature  is  a  plain  deduction 


374  HOW  CROPS  GROW. 

from  the  fact  that  the  leaves  within  were  found  wilted 
in  the  morning,  while  they  recovered  toward  uoon,  al- 
though the  temperature  of  the  air  without  remained 
below  freezing.  The  wilting  was  no  doubt  chiefly  due 
to  the  diminished  power  of  the  stem  to  transmit  water  ; 
the  return  of  the  leaves  to  their  normal  condition  was 
probably  the  consequence  of  the  warming  of  the  stem  by 
the  sun's  radiant  heat.* 

One  mode  in  which  changes  of  temperature  in  the 
trunk  influence  the  flow  of  sap  is  very  obvious.  The 
wood-cells  contain,  not  only  water,  but  air.  Both  are 
expanded  by  heat,  and  both  contract  by  cold.  Air, 
especially,  undergoes  a  decided  change  of  bulk  in  this 
way.  Water  expands  nearly  one-twentieth  in  being 
warmed  from  32°  to  212°,  and  air  increases  in  volume 
more  than  one-third  by  the  same  change  of  temperature. 
When,  therefore,  the  trunk  of  a  tree  is  warmed  by  the 
sun's  heat,  the  air  is  expanded,  exerts  a  pressure  on  the 
sap,  and  forces  it  out  of  any  wound  made  through  the 
bark  and  wood-cells.  It  only  requires  a  rise  of  tempera- 
ture to  the  extent  of  a  few  degrees  to  occasion  from  this 
cause  alone  a  considerable  flow  of  sap  from  a  large  tree. 
(Hartig.) 

If  we  admit  that  water  continuously  enters  the  deep- 
lying  roots  whose  temperature  and  absorbent  power  must 
remain,  for  the  most  part,  invariable  from  day  to  day, 
we  should  have  a  constant  slow  escape  of  sap  from  the 
trunk  were  the  temperature  of  the  latter  uniform  and 
sufficiently  high.  This  really  happens  at  times  during 
every  sugar-season.  When  the  trunk  is  cooled  down  to 
the  freezing  point,  or  near  it,  the  contraction  of  air  and 
water  in  the  tree  makes  a  vacuum  there,  sap  ceases  to 
flow,  and  air  is  sucked  in  through  the  spile ;  as  the  trunk 

*  The  temperature  of  the  air  is  not  always  a  sure  indication  of  that 
of  the  solid  bodies  which  it  surrounds.  A  thermometer  will  often  rise 
by  exposure  of  the  bulb  to  the  direct  rays  of  the  sun,  30  or  40°  above  its 
Indications  when  in  the  shade. 


MOTION  OF  THE    JUICE3.  375 

becomes  heated  again,  the  gaseous  and  liquid  contents  of 
the  ducts  expand,  the  flow  of  sap  is  renewed,  and  pro- 
ceeds with  increased  rapidity  until  the  internal  pressure 
passes  its  maximum. 

As  the  season  advances  and  the  soil  becomes  heated, 
the  root-power  undoubtedly  acts  with  increased  vigor 
and  larger  quantities  of  water  are  forced  into  the  trunk, 
but  at  a  certain  time  the  escape  of  sap  from  a  wound 
suddenly  ceases.  At  this  period  a  new  phenomenon 
supervenes.  The  buds  which  were  formed  the  previous 
summer  begin  to  expand  as  the  vessels  are  distended  with 
sap,  and  finally,  when  the  temperature  attains  the  proper 
range,  they  unfold  into  leaves.  At  this  point  we  have 
a  proper  motion  of  sap  in  the  tree,  whereas  before  there 
was  little  motion  at  all  in  the  sound  trunk,  and  in  the 
tapped  stem  the  motion  was  towards  the  orifice  'and 
thence  out  of  the  tree. 

The  cessation  of  flow  from  a  cut  results  from  two  cir- 
cumstances :  first,  the  vigorous  cambial  growth,  where- 
by incisions  in  the  bark  and  wood  rapidly  heal  up  ;  and, 
second,  the  extensive  evaporation  that  goes  on  from 
foliage. 

That  evaporation  of  water  from  the  leaves  often  pro- 
ceeds more  rapidly  than  it  can  be  supplied  by  the  roots 
is  shown  by  the  facts  that  the  delicate  leaves  of  many 
plants  wilt  when  the  soil  about  their  roots  becomes  dry, 
that  water  is  often  rapidly  sucked  into  wounds  on  the 
stems  of  trees  which  are  covered  with  foliage,  and  that 
the  proportion  of  water  in  the  wood  of  the  trees  of  tem- 
perate latitudes  is  least  in  the  months  of  May,  June,  and 
July. 

Evergreens  do  not  bleed  in  the  spring-time.  The  oak 
loses  little  or  no  sap,  and  among  other  trees  great  diver- 
sity is  noticed  as  to  the  amount  of  water  that  escapes  at 
a  wound  on  the  stem.  In  case  of  evergreens  we  have  a 
stem  destitute  of  all  proper  vascular  tissue,  and  admit- 


376  HOW  CROPS  GROW. 

ting  a  flow  of  liquid  only  through  perforations  of  the 
wood-cells,  if  theae  really  exist  (which  Sachs  denies). 
Again,  the  leaves  admit  of  continual  evaporation,  and 
furnish  an  outlet  to  the  water.  The  colored  heart-wood 
existing  in  many  trees  is  impervious  to  water,  as  shown 
by  the  experiments  of  Boucherie  and  Hartig.  Sap  can 
only  flow  through  the  white,  so-called  sap-wood.  In 
early  June,  the  new  shoots  of  the  vine  do  not  bleed  when 
cut,  nor  does  sap  flow  from  the  wounds  made  by  break- 
ing them  off  close  to  the  older  stem,  although  a  gash  in 
the  latter  bleeds  profusely.  In  the  young  branches, 
there  are  no  channels  that  permit  the  rapid  efflux  of 
water. 

Composition  of  Sap. — The  sap  in  all  cases  consists 
chiefly  of  water.  This  liquid,  as  it  is  absorbed,  brings 
in  from  the  soil  a  small  proportion  of  certain  saline  mat- 
ters— the  phosphates,  sulphates,  nitrates,  etc.,  of  potas- 
sium, calcium,  and  magnesium.  It  finds  in  the  plant 
itself  its  organic  ingredients.  These  may  be  derived 
from  matters  stored  in  reserve  during  a  previous  year,  as 
in  the  spring  sap  of  trees ;  or  may  be  newly  formed,  as 
in  summer  growth. 

The  sugar  of  maple-sap,  in  spring,  is  undoubtedly  pro- 
duced by  the  transformation  of  starch  which  is  found 
abundantly  in  the  wood  in  winter.  According  to  Hartig 
(Jour,  fttr  Prakt.  Ch.,  5,  p.  217,  1835),  all  deciduous 
trees  contain  starch  in  their  wood  and  yield  a  sweet 
spring  sap,  while  evergreens  contain  little  or  no  starch. 
Hartig  reports  having  been  able  to  procure  from  the  root- 
wood  of  the  horse-chestnut  in  one  instance  no  less  than 
26  per  cent  of  starch.  This  is  deposited  in  the  tissues 
during  summer  and  autumn,  to  be  dissolved  for  the  use 
of  the  plant  in  developing  new  foliage.  In  evergreens 
and  annual  plants  the  organic  matters  of  the  sap  are 
derived  more  directly  from  the  foliage  itself.  The  leaves 
absorb  carbon  dioxide  and  unite  its  carbon  to  the  eler 


MOTION  OF  THE   JUICES.  37T 

ments  of  water,  with  the  production  of  sugar  and  other 
carbhydrates.  In  the  leaves,  also,  probably  nitrogen 
from  the  nitrates  and  ammonia-salts  gathered  by  the 
roots,  is  united  to  carbon,  hydrogen,  and  oxygen,  in  the 
formation  of  albuminoids. 

Besides  sugar,  malic  acid  and  minute  quantities  of 
proteids  exist  in  maple  sap.  Towards  the  close  of  the 
sugar-season  the  sap  appears  to  contain  other  organic 
substances  which  render  the  sugar  impure,  brown  in 
color,  and  of  different  flavor. 

It  is  a  matter  of  observation  that  maple-sugar  is  whiter, 
purer,  and  "  grains  "  or  crystallizes  more  readily  in  those 
years  when  spring-rains  or  thaws  are  least  frequent. 
This  fact  would  appear  to  indicate  that  the  brown  or- 
ganic matters  which  water  extracts  from  leaf -mold  may 
enter  the  roots  of  the  trees,  as  is  the  belief  of  practical 
men. 

The  spring-sap  of  many  other  deciduous  trees  of  tem- 
perate climates  contains  sugar,  but  while  it  is  cane  sugar 
in  the  maple,  in  other  trees  it  appears  to  consist  mostly 
or  entirely  of  dextrose. 

Sugar  is  the  chief  organic  ingredient  in  the  juice  of 
the  sugar  cane,  Indian  corn,  beet,  carrot,  turnip,  and 
parsnip. 

The  sap  that  flows  from  the  vine  and  from  many  cul- 
tivated herbaceous  plants  contains  little  or  no  sugar ;  in 
that  of  the  vine,  gum  or  dextrin  is  found  in  its  stead. 

What  has  already  been  stated  makes  evident  that  we 
cannot  infer  the  quantity  of  sap  in  a  plant  from  what 
may  run  out  of  an  incision,  for  the  sap  that  thus  issues 
is  for  the  most  part  water  forced  up  from  the  soil.  It  is 
equally  plain  that  the  sap,  thus  collected,  has  not  the 
normal  composition  of  the  juices  of  the  plant ;  it  must 
be  diluted,  and  must  be  the  more  diluted  the  longer  and 
the  more  rapidly  it  flows. 

Ulbricht  has  made  partial  analyses  of  the  sap  obtained 


378  HOW  CHOPS  GROW. 

from  the  stumps  of  potato,  tobacco,  and  sun-flower 
plants.  He  found  that  successive  portions,  collected 
separately,  exhibited  a  decreasing  concentration.  In 
sunflower  sap,  gathered  in  fiye  successive  portions,  the 
liter  contained  the  following  quantities  (grams)  of  solid 
matter : 

1.  2.  3.  4.  5. 

Volatile  substance,...  1.45  0.60  0.30  0.25  0.21 

Ash, 1.58  1.66  1.18  0.70  0.60 

Total, sioi  2il6  7*8  0.95  O81 

The  water  which  streams  from  a  wound  dissolves  and 
carries  forward  with  it  matters  that,  in  the  uninjured 
plant,  would  probably  suffer  a  much  less  rapid  and  ex- 
tensive translocation.  From  the  stump  of  a  potato-stalk 
would  issue,  by  the  mere  mechanical  effect  of  the  flow  of 
water,  substances  generated  in  the  leaves,  whose  proper 
movement  in  the  uninjured  plant  would  be  downwards 
into  the  tubers. 

Different  Kinds  of  Sap. — It  is  necessary  at  this 
point  in  our  discussion  to  give  prominence  to  the  fact 
that  there  are  different  kinds  of  sap  in  the  plant.  As 
we  have  seen  (p.  289),  the  cross  section  of  the  plant  pre- 
sents two  kinds  of  tissue,  the  cellular  and  vascular. 
These  carry  different  juices,  as  is  shown  by  their  chemi- 
cal reactions.  In  the  cell-tissues  exist  chiefly  the  non- 
nitrogenous  principles,  sugar,  starch,  oil,  etc.  The 
liquid  in  these  cells,  as  Sachs  has  shown,  commonly  con- 
tains also  organic  acids  and  acid-salts,  and  hence  gives  a 
red  color  to  blue  litmus.  In  the  vascular  tissue  albumin- 
oids preponderate,  and  the  sap  of  the  ducts  commonly 
has  an  alkaline  reaction  towards  test  papers.  These  dif- 
ferent kinds  of  sap  are  not,  however,  always  strictly  con- 
fined to  either  tissue*  In  the  root-tips  and  buds  of 
many  plants  (maize,  squash,  onion),  the  young  (new- 
formed)  cell-tissue  is  alkaline  from  the  preponderance  of 


MOTION  OF  THE    JUICES.  370 

albuminoids,  while  the  spring  sap  flowing  from  the  ducts 
and  wood  of  the  maple  is  faintly  acid. 

In  many  plants  is  found  a  system  of  channels  (milk- 
ducts,  p.  304),  independent  of  the  vascular  bundles, 
Which  contain  an  opaque,  white,  or  yellow  juice.  This 
liquid  is  seen  to  exude  from  the  broken  stem  of  the  milk- 
weed (Asdepias),  of  lettuce,  or  of  celandine  (Chelidon- 
ium),  and  may  be  noticed  to  gather  in  drops  upon  a 
fresh-cut  slice  of  the  sweet  potato.  The  milky  juice 
often  differs,  not  more  strikingly  in  appearance  than  it 
does  in  taste,  from  the  transparent  sap  of  the  cell-tissue 
and  vascular  bundles.  The  former  is  commonly  acrid 
and  bitter,  while  the  latter  is  sweet  or  simply  insipid  to 
the  tongue. 

Motion  of  the  Nutrient  Matters  of  the  Plant. — 
The  occasional  rapid  passage  of  a  current  of  water  up 
wards  through  the  plant  must  not  be  confounded  with 
the  normal,  necessary,  and  often  contrary  motion  of  the 
nutrient  matters  out  of  which  new  growth  is  organized, 
but  is  an  independent  or  highly  subordinate  process  by 
which  the  plant  adapts  itself  to  the  constant  changes 
that  are  taking  place  in  the  soil  and  atmosphere  as  re- 
gards their  content  of  moisture. 

A  plant  supplied  with  enough  moisture  to  keep  its  tis- 
sues turgid  is  in  a  normal  state,  no  matter  whether  the 
water  Avithin  it  is  nearly  free  from  upward  flow  or  ascends 
rapidly  to  compensate  the  waste  by  evaporation.  In 
both  cases  the  motion  of  the  matters  dissolved  in  the  sap 
is  nearly  the  same.  In  both  cases  the  plant  develops 
nearly  alike.  In  both  cases  the  nutritive  matters  gath- 
ered at  the  root- tips  ascend,  and  those  gathered  by  the 
leaves  descend,  being  distributed  to  every  growing  cell ; 
and  these  motions  are  comparatively  independent  of,  and 
but  little  influenced  by,  the  motion  of  the  water  in  which 
they  are  dissolved. 

Tb<e  upward  flow  of  sap  in  the  plant  is  confined  to  the 


380  HOW  CHOPS  GROW. 

vascular  bundles,  whether  these  are  arranged  symmetri* 
cally  and  compactly,  as  in  exogenous  plants,  or  distrib- 
uted singly  through  the  stem,  as  in  the  endogens.  This 
is  not  only  seen  upon  a  bleeding  stump,  but  is  made  evi- 
dent by  the  oft-observed  fact  that  colored  liquids,  when 
absorbed  into  a  plant  or  cutting,  visibly  follow  the  course 
of  the  vessels,  though  they  do  not  commonly  penetrate 
the  spiral  ducts,  but  ascend  in  the  sieve-cells  of  the  cam- 
bium.* 

The  rapid  supply  of  water  to  the  foliage  of  a  plant, 
either  from  the  roots  or  from  a  vessel  in  which  the  cut 
stem  is  immersed,  goes  on  when  the  cellular  tissues  of 
the  bark  and  pith  are  removed  or  interrupted,  but  is  at 
once  checked  by  severing  the  vascular  bundles. 

The  proper  motion  of  the  nutritive  matters  in  the 
plant — of  the  salts  disssolved  from  the  soil  and  of  the 
organic  principles  compounded  from  carbonic  acid,  water, 
and  nitric  acid  or  ammonia  in  the  leaves — is  one  of  slow 
diffusion,  mostly  through  the  walls  of  imperforate  cells, 
and  goes  on  in  all  directions.  New  growth  is  the  forma- 
tion and  expansion  of  new  cells  into  which  nutritive 
substances  are  imbibed,  but  not  poured  through  visible 
passages.  When  closed  cells  are  converted  into  ducts  or 
visibly  communicate  with  each  other  by  pores,  their  ex- 
pansion has  ceased.  Henceforth  they  merely  become 
thickened  by  interior  deposition. 

Movements  of  Nutrient  Matters  in  the  Bark  or 
Rind. — The  ancient  observation  of  what  ordinarily  ensues 
when  a  ring  of  bark  is  removed  from  the  stem  of  an  exo- 
genous tree,  led  to  the  erroneous  assumption  of  a  form- 
al downward  current  of  "  elaborated  "  sap  in  the  bark. 
When  a  cutting  from  one  of  our  common  trees  is  girdled 
at  its  middle  and  then  placed  in  circumstances  favorable 


*  As  in  Unger's  experiment  of  placing  a  hyacinth  In  the  juice  of  the 
poke  weed  (/'hytolnccu),  or  in  Hallier's observations  on  cuttings  dipped 
jn  cherry-juice.  (Fs.  <!>£.,  IX,  p.  1.) 


MOTION  OF  THE    JUICES. 


381 


Fig.  01 


for  growth,  as  in  moist,  warm 
air,  with  its  lower  extremity 
in  water,  roots  form  chiefly 
at  the  edge  of  the  bark  just 
above  the  removed  ring.  The 
twisting,  or  half -breaking,  as 
well  as  ringing  of  a  layer, 
promotes  the  development  of 
roots.  Latent  buds  are  often 
called  forth  on  the  stems  of 
fruit  trees,  and  branches  grow 
more  vigorously,  by  making 
a  transverse  incision  through 
the  bark  just  below  the  point 
of  their  issue.  Girdling  a 
fruit-bearing  branch  of  the 
grape-vine  near  its  junction 
with  the  older  wood  has  the 
effect  of  greatly  enlarging  the 
fruit.  It  is  well  known  that 
a  wide  wound  made  on  the 
stem  of  a  tree  heals  up  by  the 
formation  of  new  wood,  and 
commonly  the  growth  is  most 
rapid  and  abundant  above  the 
cut.  From  these  facts  it  was 
concluded  that  sap  descends 
in  the  bark,  and,  not  being 
able  to  pass  below  a  wound, 
leads  to  the  organization  of 
new  roots  or  wood  just  above 
it. 

The  accompanying  illustration, 
Fig.  66,  represents  the  base  of  a  cut- 
ting from  an  exogenous  stem  (pear 
or  currant),  girdled  at  B  and  kept 
for  some  days  immersed  in  water  to 
the  depth  indicated  by  the  line  L. 


382  HOW  CHOPS  GROW. 

The  first  maif estation  of  growth  is  the  formation  of  a  protuberance  at 
the  lower  edge  of  the  bark,  which  is  known  to  gardeners  as  a  callous, 
C.  This  is  an  extension  of  the  cellular  tissue.  From  the  callous  shortly 
appear  rootlets,  R,  which  originate  from  the  vascular  tissue.  Rootlets 
also  break  from  the  stem  above  the  callous  and  also  above  the  water, 
if  the  air  be  moist.  They  appear,  likewise,  though  in  less  number, 
below  the  girdled  place. 

Nearly  all  the  organic  substances  (carbhydrates,  al- 
buminoids, acids,  etc.)  that  are  formed  in  a  plant  are 
produced  in  the  leaves,  and  must  necessarily  find  their 
way  down  to  nourish  the  stem  and  roots.  The  facts 
just  mentioned  demonstrate,  indeed,  that  they  do  go 
down  in  the  bark.  We  have,  however,  no  proof  that 
there  is  a  downward  flow  of  sap.  Such  a  flow  is  not 
indicated  by  a  single  fact,  for,  as  we  have  before  seen, 
the  only  current  of  water  in  the  uninjured  plant  is  the 
upward  one  which  results  from  root-action  and  evapora- 
tion, and  that  is  variable  and  mainly  independent  of  the 
distribution  of  nutritive  matters.  Closer  investigation 
has  shown  that  the  most  abundant  downward  movement 
of  the  nutrient  matters  generated  in  the  leaves  proceeds 
in  the  thin-walled  sieve-cells  of  the  cambium,  which,  in 
exogens,  is  young  tissue  common  to  the  outer  wood  and  the 
inner  bark — which,  in  fact,  unites  bark  and  wood.  The 
tissues  of  the  leaves  communicate  directly  with,  and  are 
a  continuation  of,  the  cambium,  and  hence  matters 
formed  by  the  leaves  must  move  most  rapidly  in  the 
cambium.  If  they  pass  with  greatest  freedom  through 
the  sieve-cells,  the  fact  is  simply  demonstration  that  the 
latter  communicate  most  directly  with  those  parts  of  the 
leaf  in  which  the  matters  they  conduct  are  organized. 

In  endogenous  plants  and  in  some  exogens  (Piper  me- 
dium, Amaranthus  sanguineus),  the  vascular  bundles 
containing  sieve-cells  pass  into  the  pith  and  are  not  con- 
fined to  the  exterior  of  the  stem.  Girdling  such  plants 
does  not  give  the  result  above  described.  With  them, 
roots  are  formed  chiefly  or  entirely  at  the  base  of  the 
cutting  (Hanstein),  and  not  above  the  girdled  place. 


MOTION  OF  THE    JUICES.  383 

In  all  cases,  without  exception,  the  matters  organized 
in  the  leaves,  though  most  readily  and  abundantly  mov- 
ing downwards  in  the  vascular  tissues,  are  not  confined 
to  them  exclusively.  When  a  ring  of  bark  is  removed 
from  a  tree,  the  new  cell-tissues,  as  well  as  the  vascular, 
are  interrupted.  Notwithstanding,  matters  are  trans- 
mitted downwards,  through  the  older  wood.  When  but 
a  narrow  ring  of  bark  is  removed  from  a  cutting,  roots 
often  appear  below  the  incision,  though  in  less  number, 
and  the  new  growth  at  the  edges  of  a  wound  on  the 
trunk  of  a  tree,  though  most  copious  above,  is  still  de- 
cided below — goes  on,  in  fact,  all  around  the  gash. 

Both  the  cell-tissue  and  the  vascular  thus  admit  of 
the  transport  of  the  nutritive  matters  downwards.  In 
the  former,  the  carbhydrates — starch,  sugar,  inulin — the 
fats,  and  acids,  chiefly  occur  and  move.  In  the  large 
ducts,  air  is  contained,  except  when  by  vigorous  root- 
action  the  stem  is  surcharged  with  water.  In  the  sieve- 
ducts  (cambium)  are  found  the  albuminoids,  though  not 
unmixed  with  carbhydrates.  If  a  tree  have  a  deep  gash 
cut  into  its  stem  (but  not  reaching  to  the  colored  heart- 
wood),  growth  is  not  suppressed  on  either  side  of  the 
cut,  but  the  nutritive  matters  of  all  kinds  pass  out  of  a 
vertical  direction  around  the  incision,  to  nourish  the  new 
wood  above  and  below.  Girdling  a  tree  is  not  fatal,  if 
done  in  the  spring  or  early  summer  when  growth  is  rapid, 
provided  that  the  young  cells,  which  form  externally, 
are  protected  from  dryness  and  other  destructive  influ- 
ences. An  artificial  bark,  i.  e.,  a  covering  of  cloth  or 
clay  to  keep  the  exposed  wood  moist  and  away  from  air, 
saves  the  tree  until  the  wound  heals  over.*  In  these 
cases  it  is  obvious  that  the  substances  which  commonly 
preponderate  in  the  sieve-ducts  must  pass  through  the 

*  If  the  freshly  exposed  wood  be  rubbed  or  wiped  with  a  cloth, 
whereby  the  moist  cambial  layer  (of  cells  containing  nuclei  and  capa- 
ble of  multiplying)  is  removed,  no  growth  can  occur.  Ratzeburg. 


384  HOW  CROPS  GROW. 

cell-tissue  in  order  to  reach  the  point  where  they  nourish 
the  growing  organs. 

Evidence  that  nutrient  matters  also  pass  upwards  in 
the  bark  is  furnished,  not  only  by  tracing  the  course  of 
colored  liquids  in  the  stem,  but  also  by  the  fact  that 
undeveloped  buds  perish  in  most  cases  when  the  stem  is 
girdled  between  them  and  active  leaves.  In  the  excep- 
tions to  this  rule,  the  vascular  bundles  penetrate  the 
pith,  and  thereby  demonstrate  that  they  are  the  chan- 
nels of  this  movement.  A  minority  of  these  exceptions 
again  makes  evident  that  the  sieve-cells  are  the  path  of 
transfer,  for,  as  Hanstein  has  shown,  in  certain  plants 
(SolanacesB,  Asclepiadeae,  etc.),  sieve-cells  penetrate  the 
pith  unaccompanied  by  any  other  elements  of  the  vascu- 
lar bundle,  and  girdled  twigs  of  these  plants  grow  above 
as  well  as  beneath  the  wound,  although  all  leaves  above 
the  girdled  place  be  cut  off,  so  that  the  nutriment  of  the 
buds  must  come  from  below  the  incision. 

The  substances  which  are  organized  in  the  foliage  of  a 
plant,  as  well  as  those  which  are  imbibed  by  the  roots, 
move  to  any  point  where  they  can  supply  a  want.  Garb- 
hydrates  pass  from  the  leaves,  not  only  downwards,  to 
nourish  new  roots,  but  upwards,  to  feed  the  buds,  flow- 
ers, and  fruit.  In  case  of  cereals,  the  power  of  the 
leaves  to  gather  and  organize  atmospheric  food  nearly  or 
altogether  ceases  as  they  approach  maturity.  The  seed 
grows  at  the  expense  of  matters  previously  stored  in  the 
foliage  and  stems  (p.  237),  to  such  an  extent  that  it  may 
ripen  quite  perfectly  although  the  plant  be  cut  when  the 
kernel  is  in  the  milk,  or  even  earlier,  while  the  juice  of 
the  seeds  is  still  watery  and  before  starch-grains  have 
begun  to  form. 

In  biennial  root-crops,  the  root  is  the  focus  of  motion 
for  the  matters  organized  by  growth  during  the  first 
year ;  but  in  the  second  year  the  stores  of  the  root  are 
completely  exhausted  for  the  support  of  flowers  and  seed, 


CAUSES  OF  THE  MOTION  OF  JUICES.  385 

BO  that  the  direction  of  the  movement  of  these  organized 
matters  is  reversed.  In  both  years  the  motion  of  water 
is  always  the  same,  viz.,  from  the  soil  upwards  to  the 
leaves.  * 

The  summing  up  of  the  whole  matter  is  that  the  nutri- 
ent substances  in  the  plant  are  not  absolutely  confined 
to  any  path,  and  may  move  in  any  direction.  The  fact 
that  they  chiefly  follow  certain  channels,  and  move  in 
this  or  that  direction,  is  plainly  dependent  upon  the 
structure  and  arrangement  of  the  tissues,  on  the  sources 
of  nutriment,  and  on  the  seat  of  growth  or  other  action. 


§3. 


THE    CAUSES  OF  MOTION  OF  THE  VEGETABLE    JUICES. 

Porosity  of  Vegetable  Tissues — Porosity  is  a 
property  of  all  the  vegetable  tissues  and  implies  that  the 
molecules  or  smallest  particles  of  matter  composing  the  tis- 
sues are  separated  from  each  other  by  a  certain  space.  In 
a  multitude  of  cases  bodies  are  visibly  porous.  In  many 
more  we  can  see  no  pores,  even  by  the  aid  of  the  highest 
magnifying  powers  of  the  microscope  ;  nevertheless  the 
fact  of  porosity  is  a  necessary  inference  from  another 
fact  which  may  be  observed,  viz.,  that  of  absorption.  A 
fiber  of  linen,  to  the  unassisted  eye,  has  no  pores. 
Under  the  microscope  we  6nd  that  it  is  a  tubular  cell, 
the  bore  being  much  less  than  the  thickness  of  the  walls. 
By  immersing  it  in  water  it  swells,  becomes  more  trans- 
parent, and  increases  in  weight.  If  the  water  be  colored 
by  solution  of  indigo  or  cochineal,  the  fiber  is  visibly 

*  The  motion  of  water  is  always  upwards,  because  the  soil  always 
contains  more  water  than  the  air.  If  a  plant  were  so  situated  that  its 
roots  should  steadily  lack  water  while  its  foliage  had  an  excess  of  this 
liquid,  it  cannot  be  doubted  that  then  the  "sap"  would  pass  down  in 
a  rej?ular  flow.  In  this  case,  nevertheless,  the  nutrient  matters  would 
take  their  normal  course. 

25 


386  HOW  CROPS  GROW. 

penetrated  by  the  dye.  It  is  therefore  porous,  not  only  • 
in  the  sense  of  having  an  interior  cavity  which  becomes 
visible  by  a  high  magnifying  power,  but  likewise  in  hav- 
ing throughout  its  apparently  imperforate  substance  in- 
numerable channels  in  which  liquids  can  freely  pass. 
In  like  manner,  all  the  vegetable  tissues  are  more  or  less 
penetrable  to  water. 

Imbibition  of  Liquids  by  Porous  Bodies. — Not 
oniv  do  the  tissues  of  the  plant  admit  of  the  access  of 
water  into  their  pores,  but  they  forcibly  drink  in  or 
aosoro  tnis  liquid,  when  it  is  presented  to  them  in  excess, 
until  their  pores  are  full. 

"When  the  molecules  of  a  porous  body  have  freedom 
of  motion,  they  separate  from  each  other  on  imbibing  a 
liquid  ;  the  body  itself  swells.  Even  powdered  glass  or 
fine  sand  perceptibly  increases  in  bulk  by  imbibing  water. 
Clay  swells  much  more.  Gelatinous  silica,  pectin,  gum 
tragacanth,  and  boiled  starch  hold  a  vastly  greater  amount 
of  water  in  their  pores  or  among  their  molecules. 

In  case  of  vegetable  and  animal  tissues,  or  membranes, 
we  find  a  greater  Dr  less  degree  of  expansibility  from  the 
same  cause,  but  here  the  structural  connection  of  the 
molecules  puts  a  limit  to  their  separation,  and  the  result 
of  saturating  them  with  a  liquid  is  a  state  of  turgidity 
and  tension,  which  subsides  to  one  of  yielding  flabbiness 
when  the  liquid  is  partially  removed. 

The  energy  with  which  vegetable  matters  imbibe  water 
may  be  gathered  from  a  well-known  fact.  In  granite 
quarries,  long  blocks  of  stone  are  split  out  by  driving 
plugs  of  dry  wood  into  holes  drilled  along  the  desired 
line  of  fracture  and  pouring  water  over  the  plugs.  The 
liquid  penetrates  the  wood  with  immense  force,  and  the 
toughest  rock  is  easily  broken  apart. 

The  imbibing  power  of  different  tissues  and  vegetable 
matters  is  widely  diverse.  In  general,  the  younger  or- 
gans or  parts  take  up  water  most  readily  and  freely.  The 


CAUSES  OF  THE  MOTION  OF  JUICES.  38? 

sap-wood  of  trees  is  far  more  absorbent  than  the  heart- 
wood  and  bark.  The  cuticle  of  the  leaf  is  often  com- 
paratively impervious  to  water.  Of  the  proximate  ele- 
ments we  have  cellulose  and  starch-grains  able  to  retain, 
even  when  air-dry,  10  to  15%  of  water.  "Wax  and  the 
solid  fats,  as  well  as  resins,  on  the  contrary,  do  not 
greatly  attract  water,  and  cannot  easily  be  wetted  with 
it.  They  render  cellulose,  which  has  been  impregnated 
with  them,  unabsorbent. 

Those  vegetable  substances  which  ordinarily  manifest 
the  greatest  absorbent  power  for  water,  are  the  gummy 
carbhydrates  and  the  albuminoids.  In  the  living  plant 
the  protoplasmic  membrane  exhibits  great  absorbent 
power.  Of  mineral  matters,  gelatinous  silica  (Exp.  58, 
p.  137)  is  remarkable  on  account  of  its  attraction  for 
water. 

Not  only  do  different  substances  thus  exhibit  unlike 
adhesion  to  water,  but  the  same  substance  deports  itself 
variously  towards  different  liquids. 

One  hundred  parts  of  dry  ox-bladder  were  found  by 
Liebig  to  absorb  during  24  hours  : — 

268  parts  of  pure  "Water. 

133       "  "  saturated  Brine. 

38       "  "  Alcohol  (84%). 

17       "  "  Bone-oil. 

A  piece  of  dry  leather  will  absorb  either  oil  or  water, 
and  apparently  with  equal  avidity.  If,  however,  oiled 
leather  be  immersed  in  water,  the  oil  is  gradually  and 
perfectly  displaced,  as  the  farmer  well  knows  from  his 
experience  with  greased  boots.  India-rubber,  on  the 
other  hand,  is  impenetrable  to  water,  while  oil  of  tur- 
pentine is  imbibed  by  it  in  large  quantity,  causing  the 
caoutchouc  to  swell  up  to  a  pasty  mass  many  times  its 
original  bulk. 

The  absorbent  power  is  influenced  by  the  size  of  the 
pores.  Other  things  being  equal,  the  finer  these  are,  the 
greater  the  force  with  which  a  liquid  is  imbibed.  This 


388  HOW  CROPS  GROW. 

is  shown  by  what  has  been  learned  from  the  study  of  a 
kind  of  pores  whose  eifect  admits  of  accurate  measure- 
ment. A  tube  of  glass,  with  a  narrow,  uniform  caliber, 
is  such  a  pore.  In  a  tube  of  1  millimeter  (about  ^  of 
an  inch),  in  diameter,  water  rises  30  mm.  In  a  tube  of 
-fa  millimeter,  the  liquid  ascends  300  mm.  (about  11 
inches)  ;  and,  in  a  tube  of  T£T  mm.,  a  column  of  3,000 
mm.  is  sustained.  In  porous  bodies,  like  chalk,  plaster 
stucco,  closely  packed  ashes  or  starch,  Jamin  found  that 
water  was  absorbed  with  force  enough  to  overcome  the 
pressure  of  the  atmosphere  from  three  to  six  times ;  in 
other  words,  to  sustain  a  column  of  water  in  a  wide 
tube  100  to  200  ft.  high.  (Comptes  Rendus,  50,  p.  311.) 

Absorbent  power  is  influenced  by  temperature.  Warm 
water  is  absorbed  by  wood  more  quickly  and  abundantly 
than  cold.  In  cold  water  starch  does  not  swell  to  any 
striking  or  eyen  perceptible  degree,  although  consider- 
able liquid  is  imbibed.  In  hot  water,  however,  the  case 
is  remarkably  altered.  The  starch-grains  are  forcibly 
burst  open,  and  a  paste  or  jelly  is  formed  that  holds 
many  times  its  weight  of  water.  (Exp.  27,  p.  51.)  On 
freezing,  the  particles  of  water  are  mostly  withdrawn 
from  their  adhesion  to  the  starch.  The  ascent  of  liquids 
in  narrow  tubes  whose  walls  are  unabsorbent,  is,  on  the 
contrary,  diminished  by  a  rise  of  temperature. 

Adhesive  Attraction. — The  absorption  of  a  liquid 
into  the  cavities  of  a  porous  body,  as  well  as  its  rise  in  a 
narrow  tube,  are  expressions  of  the  general  fact  that 
there  is  an  attraction  between  the  molecules  of  the  liquid 
and  the  solid.  In  its  simplest  manifestation  this  attrac- 
tion exhibits  itself  as  Adhesion,  and  this  term  we  shall 
employ  to  designate  the  kind  of  force  under  considera- 
tion. If  a  clean  plate  of  glass  be  dipped  in  water,  the 
liquid  touches,  and  sticks  to,  the  glass.  On  withdraw- 
ing the  glass,  a  film  of  water  comes  away  with  it — the 
adhesive  force  of  water  to  glass  being  greater  than  the 
cohesive  force  among  the  water  molecules. 


CAUSES  OF  THE  MOTION  OF  JUICES.  389 

Capillary  Attraction. — If  two  squares  of  glass  be 
set  up  together  upon  a  plate,  so  that  they  shall  be 
in  contact  at  their  vertical  edges  on  one  side,  and  one- 
eighth  of  an  inch  apart  on  the  other,  it  will  be  seen,  on 
pouring  a  little  water  upon  the  plate,  that  this  liquid 
rises  in  the  space  between  them  to  a  hight  of  several 
inches  where  they  are  in  very  near  proximity,  and  curves 
downwards  to  their  base  where  the  interval  is  large. 

Capillary  attraction,  which  thus  causes  liquids  to  rise 
in  narrow  channels  or  fine  tubes,  involves  indeed  the 
adhesion  of  the  liquid  to  the  walls  of  the  tube,  but  also 
depends  on  a  tension  of  the  surface  of  the  liquid,  due  to 
the  fact  that  the  molecules  at  the  surface  only  attract 
and  are  only  attracted  by  underlying  molecules,  so  that 
they  exert  a  pressure  on  the  mass  of  liquid  beneath  them. 
Where  the  liquid  adheres  to  the  sides  of  a  containing 
tube  or  cavity,  this  pressure  is  diminished  and  there  the 
liquid  rises. 

Adhesion  may  be  a  Cause  of  Continual  Move- 
ment under  certain  circumstances.  When  a  new  cotton 
wick  is  dipped  into  oil,  the  motion  of  the  oil  may  be  fol- 
lowed by  the  eye,  as  it  slowly  ascends,  until  the  pores 
are  filled  and  motion  ceases.  Any  cause  which  removes 
oil  from  the  pores  at  the  apex  of  the  wick  will  disturb 
the  equilibrium  which  had  been  established  between  the 
solid  and  the  liquid.  A  burning  match  held  to  the 
wick,  by  its  heat  destroys  the  oil,  molecule  after  mole- 
cule, and  this  process  becomes  permanent  when  the  wick 
is  lighted.  As  the  pores  at  the  base  of  the  flame  give  up 
oil  to  the  latter,  they  fill  themselves  again  from  the 
pores  beneath,  and  the  motion  thus  set  up  propagates 
itself  to  the  oil  in  the  vessel  below  and  continues  as  long 
as  the  flame  burns  or  the  oil  holds  out. 

We  get  a  further  insight  into  the  nature  of  this  motion 
when  we  consider  what  happens  after  the  oil  has  all  been 
sucked  up  into  the  wick.  Shortly  thereafter  the  dimen- 


390  HOW  CROPS  GROW. 

fiions  of  the  flame  are  seen  to  dimmish.  It  does  not, 
however,  go  out,  but  burns  on  for  a  time  with  continually 
decreasing  vigor.  When  the  supply  of  liquid  in  the  por- 
ous body  is  insufficient  to  saturate  the  latter,  there  is 
Btill  the  same  tendency  to  equalization  and  equilibrium. 
If,  at  last,  when  the  flame  expires,  because  the  combus- 
tion of  the  oil  falls  below  that  rate  which  is  needful  to 
generate  heat  sufficient  to  decompose  it,  the  wick  be 
placed  in  contact  at  a  single  point,  with  another  dry 
wick  of  equal  mass  and  porosity,  the  oil  remaining  in 
the  first  will  enter  again  into  motion,  will  pass  into  the 
second  wick,  from  pore  to  pore,  until  the  oil  has  been 
shared  nearly  equally  between  them. 

In  case  of  water  contained  in  the  cavities  of  a  porous 
body,  evaporation  from  the  surface  of  the  latter  becomes 
remotely  the  cause  of  a  continual  upward  motion  of  the 
liquid. 

The  exhalation  of  water  as  vapor  from  the  foliage  of  a 
plant  thus  necessitates  the  entrance  of  water  as  liquid 
at  the  roots,  and  maintains  a  flow  of  it  in  the  sap-ducts, 
or  causes  it  to  pass  by  absorption  from  cell  to  cell. 

Liquid  Diffusion. — The  movements  that  proceed  in 
plants,  when  exhalation  is  out  of  the  question,  viz.,  such 
as  are  manifested  in  the  stump  of  a  vine  cemented  into  a 
gauge  (Fig.  43,  p.  248),  are  not  to  be  accounted  for  by 
capillarity  or  mere  absorptive  force  under  the  conditions 
as  yet  noticed.  To  approach  their  elucidation  we  require 
to  attend  to  other  considerations. 

The  particles  of  many  different  kinds  of  liquids  attract 
each  other.  Water  and  alcohol  may  be  mixed  together 
in  all  proportions  in  virtue  of  their  adhe-ive  attraction. 
If  we  fill  a  vial  with  water  to  the  rim  and  carefully  lower 
it  to  the  bottom  of  a  tall  jar  of  alcohol,  we  shall  find 
after  some  hours  that  alcohol  has  penetrated  the  vial, 
and  water  has  passed  out  into  the  jar,  notwithstanding 
the  latter  liquid  is  considerably  heavier  than  the  former. 


CAUSES  OF  THE  MOTION   OF  JUICES.  391 

If  the  water  be  colored  by  indigo  or  cherry  juice,  its 
motion  may  be  followed  by  the  eye,  and  after  a  certain 
lapse  of  time  the  water  and  alcohol  will  be  seen  to  have 
become  uniformly  mixed  throughout  the  two  vessels. 
This  manifestation  of  adhesive  attraction  is  termed  Liq- 
uid Diffusion. 

What  is  true  of  two  liquids  likewise  holds  for  two 
solutions,  i.  e.,  for  two  solids  made  liquid  by  the  action 
of  a  solvent.  A  vial  filled  with  colored  brine,  or  syrup, 
and  placed  in  a  vessel  of  water,  will  discharge  its  con- 
tents into  the  latter,  itself  receiving  water  in  return ; 
and  this  motion  of  the  liquids  will  not  cease  until  the 
whole  is  uniform  in  composition,  i.  e.,  until  every  mole- 
cule of  salt  or  sugar  is  equally  attracted  by  all  the  mole- 
cules of  water. 

When  several  or  a  large  number  of  soluble  substances 
are  placed  together  in  water,  the  diffusion  of  each  one 
throughout  the  entire  liquid  will  go  on  in  the  same  way 
until  the  mixture  is  homogeneous. 

Liquid  Diffusion  may  be  a  Cause  of  Continual 
Movement  whenever  circumstances  produce  continual 
disturbances  in  the  composition  of  a  solution  or  in  that 
of  a  mixture  of  liquids. 

If  into  a  mixture  of  two  liquids  we  introduce  a  solid 
body  which  is  able  to  combine  chemically  with,  and 
solidify  one  of  the  liquids,  the  molecule?  of  this  liquid 
will  begin  to  move  toward  the  solid  body  from  all  points, 
and  this  motion  will  cease  only  when  the  solid  is  able  to 
combine  with  no  more  of  the  one  liquid,  or  no  more 
remains  for  it  to  unite  with.  Thus,  when  quicklime  is 
placed  in  a  mixture  of  alcohol  and  water,  the  water  is  in 
time  completely  condensed  in  the  lime,  and  the  alcohol 
is  rendered  anhydrous. 

Rate  of  Diffusion. — The  rate  of  diffusion  varies  with 
the  nature  of  the  liquids  ;  if  solutions,  with  their  degree 
of  concentration  and  with  the  temperature. 


392  HOW  CROPS  GROW. 

Colloids  and  Crystalloids. — There  is  a  class  of  bodies 
whose  molecules  are  singularly  inactive  in  many  respects, 
and  have,  when  dissolved  in  water  or  other  liquid,  a 
very  low  capacity  for  diffusive  motion.  These  bodies 
are  termed  Colloids,*  and  are  characterized  by  swelling 
up  or  uniting  with  water  to  bulky  masses  (hydrates)  of 
gelatinous  consistence,  by  inability  to  crystallize,  and  by 
feeble  and  poorly-defined  chemical  affinities.  Starch, 
dextrin,  the  gums,  the  albuminoids,  pectin  and  pectic 
acid,  gelatin  (glue),  tannin,  the  hydroxides  of  iron  and 
aluminium  and  gelatinous  silica,  are  colloids.  Opposed 
to  these,  in  the  properties  just  specified,  are  those  bodies 
which  crystallize,  such  as  saccharose,  glucose,  oxalic, 
citric,  and  tartaric  acids,  and  the  ordinary  salts. 

Other  bodies  which  have  never  been  seen  to  crystallize 
have  the  same  high  diffusive  rate  ;  hence  the  class  is 
termed  by  Graham  Crystalloids,  f 

Colloidal  bodies,  when  insoluble,  are  capable  of  imbib- 
ing liquids,  and  admit  of  liquid  diffusion  through  their 
molecular  interspaces.  Insoluble  crystalloids  are,  on 
the  other  hand,  impenetrable  to  liquids  in  this  sense. 
The  colloids  swell  up  more  or  less,  often  to  a  great  bulk, 
from  absorbing  a  liquid ;  the  volume  of  a  crystalloid 
admits  of  no  such  change. 

In  his  study  of  the  rates  of  diffusion  of  various  sub- 
stances, dissolved  in  water  to  the  extent  of  one  per  cent 
of  the  liquid,  Graham  found  the  following 

APPBOXIMATE  TIMES  OF  EQUAL    DIFFUSION. 

Hydrochloric  acid,  Crystalloid,  1. 

Sodium  Chloride,  "            2J. 

Cane  Sugar,  "            7. 

Magnesium  Sulphate,  "           7. 

Albumin,  Colloid,     49. 

Caramel,  "          98. 

*  From  two  Greek  words  which  signify  glue-like. 

t  We  have  already  employed  the  word  Crystalloid  to  distinguish  the 
amorphous  albuminoids  from  their  modifications  or  combinations 
which  present  the  aspect  of  crystals  (p.  107).  This  use  of  the  word  was 
proposed  by  Nageli,  m  1862.  Graham  liad  employed  it,  as  opposed  to 
colloid,  in  1861. 


CAUSES  OF  THE  MOTION  OF  JUICES.  393 

The  table  shows  that  the  diffusive  activity  of  hydro- 
chloric acid  through  water  is  98  times  as  great  as  that  of 
caramel  (see  p.  66,  Exp.  29).  In  other  words,  a  mole- 
cule of  the  acid  will  travel  98  times  as  far  in  a  given 
time  as  the  molecule  of  caramel. 

Osmose,*  or  Membrane  Diffusion. — When  two 
miscible  liquids  or  solutions  are  separated  by  a  porous 
diaphragm,  the  phenomena  of  diffusion  (which  depend 
upon  the  mutual  attraction  of  the  molecules  of  the  dif- 
ferent liquids  or  dissolved  substances)  are  complicated 
with  those  of  imbibition  or  capillarity,  and  of  chemical 
affinity.  The  adhesive  or  other  force  which  the  septum 
is  able  to  exert  upon  the  liquid  molecules  supervenes 
upon  the  mere  diffusive  tendency,  and  the  movements 
may  suffer  remarkable  modifications. 

If  we  should  separate  pure  water  and  a  solution  of 
common  salt  by  a  membrane  upon  whose  substance  these 
liquids  could  exert  no  action,  the  diffusion  would  pro- 
ceed to  the  same  result  as  were  the  membrane  absent. 
Molecules  of  water  would  penetrate  the  membrane  on 
one  side  and  molecules  of  salt  on  the  other,  until  the 
liquid  should  become  alike  on  both.  Should  the  water 
move  faster  than  the  salt,  the  volume  of  the  brine  would 
increase,  and  that  of  the  water  would  correspondingly 
diminish.  Were  the  membrane  fixed  in  its  place,  a 
change  of  level  of  the  liquids  would  occur.  Graham  has 
observed  that  common  salt  actually  diffuses  into  water, 
through  a  thin  membrane  of  ox-bladder  deprived  of  its. 
outer  muscular  coating,  at  very  nearly  the  same  rate  as 
when  no  membrane  is  interposed. 

Dutrochet  was  the  first  to  study  the  phenomena  of 
membrane  diffusion.  He  took  a  glass  funnel  with  a  long 
and  slender  neck,  tied  a  piece  of  bladder  over  the  wide 
opening,  inverted  it,  poured  in  brine  until  the  funnel 
was  filled  to  the  neck,  and  immersed  the  bladder  in  a 

*  From  a  Greefc  word  meaning  impulsion. 


394 


HOW   CROPS   GROW. 


vessel  of  water.  He  saw  the  liquid  rise  in  the  narrow 
tube  and  fall  in  the  outer  vessel.  He  designated  the 
passage  of  water  into  the  funnel  as  endosmose,  or  inward 
propulsion.  At  the  same  time  he  found  the  water  sur- 
rounding the  funnel  to  acquire  the  taste  of  salt.  The 
outward  transfer  of  salt  was  his  exosmose.  The  more 
general  word,  Osmose,  expresses  hoth  phenomena  ;  we 
may,  however,  employ  Dutrochet's 
terms  to  designate  the  direction  of 
osmose. 

Osmometer. — When  the  apparatus 
employed  by  Dutrochet  is  so  con- 
structed that  the  diameter  of  the  nar- 
row tube  has  a  known  relation  to,  is, 
for  example,  exactly  one-tenth  that  of 
the  membrane,  and  the  narrow  tube 
itself  is  provided  with  a  millimeter 
scale,  we  have  the  Osmometer  of  Grah- 
am, Fig  G7.  The  ascent  or  descent  of 
the  liquid  in  the  tube  gives  a  measure 
of  the  amount  of  osmose,  provided  the 
hydrostatic  pressure  is  counterpoised 
by  making  the  level  of  the  liquid  with- 
in and  without  equal,  for  which  pur- 
pose water  is  poured  into  or  removed  from  the  outer  ves- 
sel. Graham  designates  the  increase  of  volume  in  the 
osmometer  as  'positive  osmose,  or  simply  osmose,  and  dis- 
tinguishes the  fall  of  liquid  in  the  narrow  tube  as  nega- 
tive osmose. 

In  the  figure,  the  external  vessel  is  intended  for  the  reception  of 
water.  The  funnel-shaped  interior  vessel  is  closed  below  with  mem- 
brane, and  stands  upon  a  shelf  of  perforated  zinc  for  support.  The 
graduated  tube  fits  the  neck  of  the  funnel  by  a  ground  joint. 

Action  of  the  Membrane. — When  an  attraction  exists 
the  membrane  itself  and  one  or  more  of  the  substances 
between  which  it  is  interposed,  then  the  rate,  amount, 
and  even  direction,  of  diffusion  may  be  greatly  changed. 


Fig.  67. 


CAUSES  OF  THE  MOTION  OF  JUICES.  395 

Water  is  imbibed  by  the  membrane  of  bladder  much 
more  freely  than  alcohol ;  on  the  other  hand,  a  film  of 
collodion  (cellulose  nitrate  left  from  the  evaporation  of 
its  solution  in  ether)  is  penetrated  much  more  easily  by 
alcohol  than  by  water.  If,  now,  these  liquids  be  sepa- 
rated by  bladder,  the  apparent  flow  will  be  towards  the 
alcohol ;  but  if  a  membrane  of  collodion  divide  them, 
the  more  rapid  motion  will  be  into  the  water. 

When  a  vigorous  chemical  action  is  exerted  upon  the 
membrane  by  the  liquid  or  the  dissolved  matters,  osmose 
is  greatly  heightened.  In  experiments  with  a  septum  of 
porous  earthenware  (porcelain  biscuit),  Graham  found 
that  in  case  of  neutral  organic  bodies,  as  sugar  and  alco- 
hol, or  neutral  salts,  like  the  alkali-chlorides  and  nitrates, 
very  little  osmose  is  exhibited,  i.  e.,  the  diffusion  is  not 
perceptibly  greater  than  it  would  be  in  absence  of  the 
porous  diaphragm. 

The  acids, — oxalic,  nitric,  and  hydrochloric, — mani- 
fest a  sensible  but  still  moderate  osmose.  Sulphuric 
and  phosphoric  acids,  and  salts  having  a  decided  alka- 
line or  acid  reaction,  viz.,  acid  potassium  oxalate,  sodi- 
um phosphate,  and  carbonates  of  potassium  and  sodium, 
exhibit  a  still  more  vigorous  osmose.  For  example,  a 
solution  of  one  part  of  potassium  carbonate  in  1,000 
parts  of  water  gains  volume  rapidly,  and  to  one  part  of 
the  salt  that  passes  into  the  water  500  parts  of  water 
enter  the  solution. 

In  all  cases  where  diffusion  is  greatly  modified  by  a 
membrane,  the  membrane  itself  is  strongly  attacked  and 
altered,  or  dissolved,  by  the  liquids.  When  animal 
membrane  is  used,  it  constantly  undergoes  decomposi- 
tion and  its  osmotic  action  is  exhaustible.  In  case 
earthenware  is  employed  as  a  diaphragm,  portions  of  its 
calcium  and  aluminium  are  always  attacked  and  dis- 
solved by  the  solutions  upon  which  it  exerts  osmose. 

Graham  asserts  that  to  induce  osmose  in  bladder,  the 


396  HOW  CHOPS  GBOW. 

chemical  action  on  the  membrane  must  be  different  on 
the  two  sides,  and  apparently  not  in  degree  only,  but 
also  in  kind,  viz.,  an  alkaline  action  on  the  albuminoid 
substance  of  the  membrane  on  the  one  side,  and  an  acid 
action  on  the  other.  The  water  appears  always  to  accu- 
mulate on  the  alkaline  or  basic  side  of  the  membrane. 
Hence,  with  an  alkaline  salt,  like  potassium  carbonate, 
in  the  osmometer,  and  water  outside,  the  flow  is  inwards  ; 
but  with  an  acid  in  the  osmometer,  there  is  negative 
osmose,  or  the  flow  is  outwards,  the  liquid  then  falling 
in  the  tube. 

Osmotic  activity  is  most  highly  manifested  in  such 
salts  as  easily  admit  of  decomposition  with  the  setting 
free  of  a  part  of  their  acid,  or  alkali. 

Hydration  of  the  membrane. — It  is  remarkable 
that  the  rapid  osmose  of  potassium  carbonate  and  other 
alkali-salts  is  greatly  interfered  with  by  common  salt,  is, 
in  fact,  reduced  to  almost  nothing  by  an  equal  quantity 
of  this  substance.  In  this  case  it  is  probable  that  the 
physical  effect  of  the  salt,  in  diminishing  the  power  of 
the  membrane  to  imbibe  water  (p.  393),  operates  in  a 
sense  inverse  to,  and  neutralizes  the  chemical  action  of, 
the  carbonate.  In  fact,  the  osmose  of  the  carbonate,  as 
well  as  of  all  other  salts,  acid  or  alkaline,  may  be  due  to 
their  effect  in  modifying  the  hydration,*  or  power  of  the 
membrane,  to  imbibe  the  liquid,  which  is  the  vehicle  of 
their  motion.  Graham  suggests  this  view  as  an  explana- 
tion of  the  osmotic  influence  of  colloid  membranes,  and 
it  is  not  unlikely  that  in  case  of  earthenware,  the  chem- 
ical action  may  exert  its  effect  indirectly,  viz.,  by  pro- 
ducing hydrated  silicates  from  the  burned  clay,  which 
are  truly  colloid  and  analogous  to  animal  membranes  in 
respect  of  imbibition.  Graham  has  shown  a  connection 
between  the  hydrating  effect  of  acids  and  alkalies  OB 
colloid  membranes  and  their  osmotic  rate. 

*  In  case  water  is  employed  as  the  liquid. 


CAUSES   OF   THE   MOTION   OF  JUICES.  397 

"It  is  well  known  that  fibrin,  albumin,  and  animal 
membrane  swell  much  more  in  very  dilute  acids  and 
alkalies  than  in  pure  water.  On  the  other  hand,  when 
the  proportion  of  acid  or  alkali  is  carried  beyond  a  point 
peculiar  to  each  substance,  contraction  of  the  colloid 
takes  place.  The  colloids  just  named  acquire  the  power 
of  combining  with  an  increased  proportion  of  water 
and  of  forming  higher  gelatinous  hydrates  in  conse- 
quence of  contact  with  dilute  acid  or  alkaline  reagents. 
Even  parchment-paper  is  more  elongated  in  an  alkaline 
solution  than  in  pure  water.  When  thus  hydrated 
and  dilated,  the  colloids  present  an  extreme  osmotic 
sensibility." 

An  illustration  of  membrane-diffusion  which  is  highly 
instructive  and  easy  to  produce,  is  the  following  : 
A  cavity  is  scooped  out  in  a  carrot,  as  in  Fig.  68,  so 
that  the  sides  remain  £  inch  or  so  thick, 
and  a  quantity  of  dry,  crushed  sugar  is 
introduced ;    after  some  time,  the  previ- 
ously dry  sugar  will  be  converted  into  a 
syrup  by  withdrawing  water  from  the  flesh 
of  the  carrot.     At  the  same  time  the  latter 
will  visibly  shrink  from  the  loss  of  a  por- 
tion of  its  liquid  contents.     In  this  case 
Fig.  68.       foe  small  portions  of  juice  moistening  the 
cavity  form  a  strong  solution  with  the  sugar  in  contact 
with  them,  into  which  water  diffuses  from  the  adjoining 
cells.     Doubtless,  also,  sugar  penetrates  the  parenchyma 
of  the  carrot. 

In  the  same  manner,  sugar,  when  sprinkled  over  thin- 
skinned  fruits,  shortly  forms  a  syrup  with  the  water 
which  it  thus  withdraws  from  them,  and  salt  packed 
with  fresh  meat  runs  to  brine  by  the  exosmose  of  the 
juices  of  the  flesh.  In  these  cases  the  fruit  and  the 
meat  shrink  as  a  result  of  the  loss  of  water. 
Graham  observed  gum  tragacanth,  which  is  insoluble 


398  HOW   CROPS   GROW. 

in  water,  to  cause  a  rapid  passage  of  water  through  a 
membrane  in  the  same  manner  from  its  power  of  imbibi- 
tion, although  here  there  could  be  no  exosmose  or  out- 
ward movement. 

The  application  of  these  facts  and  principles  to  explain- 
ing the  movements  of  the  liquids  of  the  plant  is  obvious. 
The  cells  and  the  tissues  composed  of  cells  furnish  pre- 
cisely the  conditions  for  the  manifestation  of  motion  by 
the  imbibition  of  liquids  and  by  simple  diffusion,  as  well 
as  by  osmose.  The  disturbances  needful  to  maintain 
motion  are  to  be  found  in  the  chemical  changes  that 
accompany  the  processes  of  nutrition.  The  substances 
that  normally  exist  in  the  vegetable  cells  are  numerous, 
and  they  suffer  remarkable  transformations,  both  in 
chemical  constitution  and  in  physical  properties.  The 
rapidly-diffusible  salts  that  are  presented  to  the  plant  by 
the  soil,  and  the  equally  diffusible  sugar  and  organic 
acids  that  are  generated  in  the  leaf-cells,  are,  in  part, 
converted  into  the  sluggish,  soluble  colloids,  soluble 
starch,  dextrin,  albumin,  etc.,  or  are  deposited  as  solid 
matters  in  the  cells  or  upon  their  walls.  Thus  the  dif- 
fusible contents  of  the  plant  not  only,  but  the  mem- 
branes which  occasion  and  direct  osmose,  are  subject  to 
perpetual  alterations  in  their  nature.  More  than  this, 
the  plant  grows  ;  new  cells,  new  membranes,  new  pro- 
portions of  soluble  and  diffusible  matters,  are  unceas- 
ingly brought  into  existence.  Imbibition  in  the  cell- 
membranes  and  their  solid,  colloid  contents,  Diffusion 
in  the  liquid  contents  of  the  individual  cells,  and  Osmose 
between  the  liquids  and  dissolved  matters  and  the  mem- 
branes, or  colloid  contents  of  the  cells,  must  unavoid- 
ably take  place. 

That  we  cannot  follow  the  details  of  these  kinds  of 
action  in  the  plant  does  not  invalidate  the  fact  of  their 
operation.  The  plant  is  so  complicated  and  presents 
such  a  number  and  variety  of  changes  in  its  growth, 


CAtTSES  OF  THE  MOTIOH  OF  JUICES.  399 

that  we  can  never  expect  to  understand  all  its  mysteries. 
From  what  has  been  briefly  explained,  we  can  compre- 
hend some  of  the  more  striking  or  obvious  movements 
that  proceed  in  the  vegetable  organism. 

Absorption  and  Osmose  in  Germination. — The 
absorption  of  water  by  the  seed  is  the  first  step  in  Ger- 
mination. The  coats  of  the  dry  seed,  when  put  into  the 
moist  soil,  imbibe  this  liquid  which  follows  the  cell-walls, 
from  cell  to  cell,  until  these  membranes  are  saturated 
and  swollen.  At  the  same  time  these  membranes  occa- 
sion or  permit  osmose  into  the  cell-cavities,  which,  dry 
before,  become  distended  with  liquid.  The  soluble  con- 
tents of  the  cells,  or  the  soluble  results  of  the  transforma- 
tion of  their  organized  matters,  diffuse  from  cell  to  cell 
in  their  passage  to  the  expanding  embryo. 

The  quantity  of  water  imbibed  by  the  air-dry  seed  commonly 
amounts  to  50  and  may  exceed  100  per  cent.  R.  Hoffmann  has  made 
observations  on  this  subject  (Vs.  St.,  VII,  p.  50).  The  absorption  was 
usually  complete  in  48  or  72  hours,  and  was  as  follows  in  case  of  certain 
agricultural  plants:— 

Per  cent.  Per  cent. 


Mustard 8.0 

Millet 25.0 

Maize 44.0 

Wheat 45.5 

Buckwheat 46.8 

Barley 48.2 

Turnip 51 .0 

Rye 57.7 


Oats 59.8 

Hemp 60.0 

Kidney  Bean 96.1 

Horse  Bean 104.0 

Pea 106.8 

Clover 117.5 

Beet 120.5 

White  Clover 126.7 


Root-Action — Absorption  at  the  roots  is  unquestion- 
ably an  osmotic  action  exercised  by  the  membrane  that 
bounds  the  young  rootlets  and  root-hairs  externally.  In 
principle  it  does  not  differ  from  the  absorption  of  water 
by  the  seed.  The  mode  in  which  it  occasions  the  sur- 
prising phenomena  of  bleeding  or  rapid  flow  of  sap  from 
a  wound  on  the  trunk  or  larger  roots  is  doubtless  essen- 
tially as  Hofmeister  first  elucidated  by  experiment. 

This  flow  proceeds  in  the  ducts  and  wood-cells. 
Between  these  and  the  soil  intervenes  loose  cell-tissue 


400 


HOW  CEOPS  GROW. 


surrounded  by  a  compacter  epidermis.  Osmose  takes 
place  in  the  epidermis  with  such  energy  as  not  only  to 
distend  to  its  utmost  the  cell-tissue,  but  to  cause  the 
water  of  the  cells  to  filter  through  their  walls,  and  thus 
gain  access  to  the  ducts.  The  latter  are  formed  in  young 
cambial  tissue,  and,  when  new,  are  very  delicate  in  their 
walls. 

Fig.  69  represents  a  simple  apparatus  by  Sachs  for 
imitating  the  supposed  mechanism  and  process  of  Eoot- 
action.  In  the  Fig.,  g  g  represents  a  short,  wide,  open 
A  glass  tube ;  at  a,  the  tube  is  tied  over  and  se- 
curely closed  by  a  piece  of  pig's  bladder ;  it  is  then 
filled  with  solution  of  sugar,  and  the  other  end, 
b,  is  closed  in  similar  manner  by  a  piece  of  parch- 
ment-paper (p.  59).  Finally  a  cap  of  India-rub- 
ber, K,  into  whose  neck  a  narrow,  bent  glass 
tube,  r,  is  fixed,  is  tied  on  over  b.  (These  join- 
ings must  be  made  very  carefully  and  firmly.) 
The  space  within  r  K  is  left  empty  of  liquid,  and 
r  the  combination  is  placed  in  a  vessel  of  water,  as 
in  the  figure.  C  represents  a  root-cell  whose 

exterior  wall  (cuticle), 
a,  is  less  penetrable 
under  pressure  than  its 
interior,  b;  r  corres- 
ponds to  a  duct  of  vas- 
cular tissue,  and  the 
surrounding  water 
takes  the  place  of  that 
Fig.  69.  existing  in  the  pores  of 

the  soil.  The  water  shortly  penetrates  the  cell,  C,  dis- 
tends the  previously  flabby  membranes,  under  the  accu- 
mulating tension  filters  through  b  into  r,  and  rises  in 
the  tube ;  where  in  Sachs's  experiment  it  attained  a 
height  of  4  or  5  inches  in  24  to  48  hours,  the  tube,  r, 
being  about  5  millimeters  wide  and  the  area  of  J,  700  sq. 


CAUSES  OP  THE  MOTION  OP  JUICES.  401 

mm.  When  we  consider  the  vast  root-surface  exposed 
to  the  soil,  in  case  of  a  vine,  and  that  myriads  of  root- 
lets and  root-hairs  unite  their  action  in  the  compara- 
tively narrow  stem,  we  must  admit  that  the  apparatus 
above  figured  gives  us  a  very  satisfactory  glance  into  the 
causes  of  bleeding. 

Motion  of  Nutritive  or  Dissolved  Matters;  Se- 
lective Power  of  the  Plant. — The  motion  of  the  sub- 
stances that  enter  the  plant  from  the  soil  in  a  state  of 
solution,  and  of  those  organized  within  the  plant  is,  to  a 
great  degree,  separate  from  and  independent  of  that 
which  the  water  itself  takes.  At  the  same  time  that 
water  is  passing  upwards  through  the  plant  to  make 
good  the  waste  by  evaporation  from  the  foliage,  sugar  or 
other  carbhydrate  generated  in  the  leaves  is  diffusing 
against  the  water,  and  finding  its  way  down  to  the  very 
root-tips.  This  diffusion  takes  place  mostly  i  i  the  cell- 
tissue,  and  is  undoubtedly  greatly  aided  by  osmose,  i.  e., 
by  the  action  of  the  membranes  themselves.  The  very 
thickening  of  the  cell- walls  by  the  deposition  of  cellulose 
would  indicate  an  attraction  for  the  material  from  which 
cellulose  is  organized.  The  same  transfer  goes  on  sim- 
ultaneously in  all  directions,  not  only  into  roots  and 
stem,  but  into  the  new  buds,  into  flowers  and  fruit. 
We  have  considered  the  tendency  to  equalization  between 
two  masses  of  liquid  separated  from  each  other  by  pen- 
etrable membranes.  This  tendency  makes  valid  for  the 
organism  of  the  plant  the  law  that  demand  creates  sup- 
ply. In  two  contiguous  cells,  one  of  which  contains 
solution  of  sugar,  and  the  other  solution  of  potassium 
nitrate,  these  substances  must  diffuse  until  they  are 
mingled  equally,  unless,  indeed,  the  membranes  or  some 
other  substance  present  exerts  an  opposing  and  prepon- 
derating attraction. 

In  the  simplest  phases  of  diffusion  each  substance  is, 
to  a  certain  degree,  independent  of  every  other.  Any 


402  HOW  CEOPS  GEOW. 

salt  dissolved  in  the  water  of  the  soil  must  diffuse  into 
the  root-cells  of  a  plant,  if  it  be  absent  from  the  sap  of 
this  root-cell  and  the  membrane  permit  its  passage. 
"When  the  root-cell  has  acquired  a  certain  proportion  of 
the  salt,  a  proportion  equal  to  that  in  the  soil-water, 
more  cannot  enter  it.  So  soon  as  a  molecule  of  the  salt 
has  gone  on  into  another  cell  or  been  removed  from  the 
sap  by  any  chemical  transformation,  then  a  molecule 
may  and  must  enter  from  without. 

Silica  is  much  more  abundant  in  grasses  and  cereals 
than  in  leguminous  plants.  In  the  former  it  exists  to 
the  extent  of  about  25  parts  in  1,000  of  the  air-dry  foli- 
age, while  the  leaves  and  stems  of  the  latter  contain  but 
3  parts.  When  these  crops  grow  side  by  side,  their 
roots  are  equally  bathed  by  the  same  soil- water.  Silica 
enters  both  alike,  and,  so  far  as  regards  itself,  brings 
the  cell-contents  to  the  same  state  of  saturation  that 
exists  in  the  soil.  The  cereals  are  able  to  dispose  of 
silica  by  giving  it  a  place  in  the  cuticular  cells ;  the 
leguminous  crops,  on  the  other  hand,  cannot  remove  it 
from  their  juices  ;  the  latter  remain  saturated,  and  thus 
further  diffusion  of  silica  from  without  becomes  impos- 
sible except  as  room  is  made  by  new  growth.  It  is  in 
this  way  that  we  have  a  rational  and  adequate  explana- 
tion of  the  selective  power  of  the  plant,  as  manifested 
in  its  deportment  towards  the  medium  that  invests  its 
roots.  The  same  principles  govern  the  transfer  of  mat- 
ters from  cell  to  cell,  or  from  organ  to  organ,  within  the 
plant.  Wherever  there  is  unlike  composition  of  two 
miscible  juices,  diffusion  is  thereby  set  up,  and  proceeds 
as  long  as  the  cause  of  disturbance  lasts,  provided  im- 
penetrable membranes  do  not  intervene.  The  rapid 
movement  of  water  goes  on  because  there  is  great  loss  of 
this  liquid ;  the  slow  motion  of  silica  is  a  consequence 
of  the  little  use  that  arises  for  it  in  the  plant. 

Strong  chemical  affinities  may  be  overcome  by  help  of 


CAUSES  Of  ffiE  MOflOtf  OF  JUICES.  403 

osmose.  Graham  long  ago  observed  the  decomposition 
of  alum  (sulphate  of  aluminium  and  potassium)  by  mere 
diffusion  ;  its  potassium  sulphate  having  a  higher  diffu- 
sive rate  than  its  aluminium  sulphate.  In  the  same 
manner  acid  potassium  sulphate,  put  in  contact  with 
water,  separates  into  neutral  potassium  sulphate  and 
Zree  sulphuric  acid.* 

We  have  seen  (pp.  170-1)  that  the  plant,  when  veg- 
etating in  solutions  of  salts,  is  able  to  decompose  them. 
It  separates  the  components  of  potassium  nitrate — appro- 
priating the  acid  and  leaving  the  base  to  accumulate  in 
the  liquid.  It  resolves  chloride  of  ammonium, — taking 
up  ammonia  and  rejecting  the  hydrochloric  acid.  The 
action  in  these  cases  we  cannot  definitely  explain,  but 
our  analogies  leave  no  doubt  as  to  the  general  nature  of 
the  agencies  that  cooperate  to  such  results. 

The  albuminoids  in  their  usual  form  are  colloid 
bodies,  and  very  slow  of  diffusion  through  liquids. 
They  pass  a  collodion  membrane  somewhat  (Schu- 
macher), but  can  scarcely  penetrate  parchment-paper 
(Graham).  In  the  plant  they  are  found  chiefly  in  the 
sieve-cells  and  adjoining  parts  of  the  cambium.  Since 
for  their  production  they  must  ordinarily  require  the 
concourse  of  a  carbhydrate  and  a  nitrate,  they  are  not 
unlikely  generated  in  the  cambium  itself,  for  here  the 
descending  carbhydrates  from  the  foliage  come  in  con- 
tact with  the  nitrates  as  they  rise  from  the  soil.  On  the 
yfcher  hand,  the  albuminoids  become  more  diffusible  in 
gome  of  their  combinations.  Schumacher  asserts  that 
carbonates  and  phosphates  of  the  alkalies  considerably 
increase  the  osmose  of  albumin  through  collodion  mem- 
branes (PhysiJc  der  Pflanzen,  p.  128).  It  is  probable  that 
those  combinations  or  modifications  of  the  albuminoids 


*Tlie  decomposition  of  these  salts  is  begun  by  the  water  in  which 
they  are  dissolved,  and  is  carried  on  by  osmose,  because  the  latter 
secures  separation  of  the  reacting  substances. 


404  fiow  CROPS  GftOW. 

which  occur  in  the  soluble  crystalloids  of  aleurone 
(p.  105)  and  haemoglobin  (p.  97)  are  highly  diffusible, 
as  certainly  is  the  case  with  the  peptones. 

Gaseous  bodies,  especially  the  carbonic  acid  and  oxy- 
gen of  the  atmosphere,  which  have  free  access  to  the 
intercellular  cavities  of  the  foliage,  and  which  are  for  the 
most  part  the  only  contents  of  the  larger  ducts,  may  be 
distributed  throughout  the  plant  by  osmose  after  having 
been  dissolved  in  the  sap  or  otherwise  absorbed  by  the 
cell-contents. 

Influence  of  the  Membranes. — The  sharp  separa- 
tion of  unlike  juices  and  soluble  matters  in  the  plant 
indicates  the  existence  of  a  remarkable  variety  and  range 
of  adhesive  attractions.  In  orange-colored  flowers  we 
see  upon  microscopic  examination  that  this  tint  is  pro- 
duced by  the  united  effect  of  yellow  and  red  pigments 
which  are  contained  in  the  cells  of  the  petals.  One  cell 
is  filled  with  yellow  pigment,  and  the  adjoining  one  with 
red,  but  these  two  colors  are  never  contained  in  the 
same  cell.  In  fruits  we  have  coloring  matters  of  great 
tinctorial  power  and  freely  soluble  in  water,  but  they 
never  forsake  the  cells  where  they  appear,  never  wander 
into  the  contiguous  parts  of  the  plant.  In  the  stems 
and  leaves  of  the  dandelion,  lettuce,  and  many  other 
plants,  a  white,  milky,  and  bitter  juice  is  contained,  but 
it  is  strictly  confined  to  certain  special  channels  and 
never  visibly  passes  beyond  them.  The  loosely  disposed 
cells  of  the  interior  of  leaves  contain  grains  of  chloro- 
phyl,  but  this  substance  does  not  appear  in  the  epidermal 
cells,  those  of  the  stomata  excepted.  Sachs  found  that 
solution  of  indigo  quickly  entered  the  roots  of  a  seedling 
bean,  but  required  a  considerable  time  to  penetrate  the 
stem.  Hallier,  in  his  experiments  on  the  absorption  of 
colored  liquids  by  plants,  noticed,  in  all  cases  when 
leaves  or  green  stems  were  immersed  in  solution  of  indigo, 
or  black-cherry  juice,  that  these  dyes  readily  passed  into 


CAUSES  OP  THE  MOTION  OF  JUICES.  405 

and  colored  the  epidermis,  the  vascular  and  cambial  tis- 
sue, and  the  parenchyma  of  the  leaf-veins,  keeping 
strictly  to  the  cell-walls,  but  in  no  instance  communi- 
cated any  color  to  the  cells  containing  chlorophyl. 
(Phytopathologie,  Leipzig,  1868,  p.  67.)  We  must  infer 
that  the  coloring  matters  either  cannot  penetrate  the 
cells  that  are  occupied  with  chlorophyl,  or  else  are  chem- 
ically transformed  into  colorless  substances  on  entering 
them. 

Sachs  has  shown  in  numerous  instances  that  the  juices 
of  the  sieve-cells  and  cambial  tissue  are  alkaline,  while 
those  of  the  adjoining  cell-tissue  are  acid  when  examined 
by  test-paper.  (Exp.  Phys.  der  Pflanzen,  p.  394.) 

When  young  and  active  cells  are  moistened  with  solu- 
tion of  iodine,  this. substance  penetrates  the  cellulose 
without  producing  visible  change,  but  when  it  acts  upon 
the  protoplasm,  the  latter  separates  from  the  outer  cell- 
wall  and  collapses  towards  the  center  of  the  cavity,  as  if 
its  contents  passed  out,  without  a  corresponding  endos- 
mose  being  possible  (p.  224). 

We  may  conclude  from  these  facts  that  the  membranes 
of  the  cells  are  capable  of  effecting  and  maintaining  the 
separation  of  substances  which  have  considerable  attrac- 
tions for  each  other,  and  obviously  accomplish  this  result 
by  exerting  their  superior  attractive  or  repulsive  force. 

The  influence  of  the  membrane  must  vary  in  character 
with  those  alterations  in  its  chemical  and  structural  con- 
stitution which  result  from  growth  or  any  other  cause. 
It  is  thus,  in  part,  that  the  assimilation  of  external  food 
by  the  plant  is  directed,  now  more  to  one  class  of 
proximate  ingredients,  as  the  carbhydrates,  and  now  to 
another,  as  the  albuminoids,  although  the  supplies  of 
food  presented  are  uniform  both  in  total  and  relative 
quantity. 

If  a  slice  of  red-beet  be  washed  and  put  into  water, 
the  pigment  which  gives  it  color  does  not  readily  dissolve 


406  HOW  CHOPS  GfitOTft 

and  diffuse  out  of  the  cells,  but  the  water  remains  coloi, 
less  for  several  days.  The  pigment  is,  however,  soluble 
in  water,  as  is  seen  at  once  by  crushing  the  beet,  where- 
by the  cells  are  forcibly  broken  open  and  their  contents 
displaced.  The  cell-membranes  of  the  uninjured  root 
are  thus  apparently  able  to  withstand  the  solvent  power 
of  water  upon  the  pigment  and  to  restrain  the  latter 
from  diffusive  motion.  Upon  subjecting  the  slice  of 
beet  to  cold  until  it  is  thoroughly  frozen,  and  then  plac- 
ing it  in  warm  water  so  that  it  quickly  thaws,  the  latter 
is  immediately  and  deeply  tinged  with  red.  The  sudden 
thawing  of  the  water  within  the  pores  of  the  cell-mem- 
brane has  in  fact  so  altered  them,  that  they  can  no 
longer  prevent  the  diffusive  tendency  of  the  pigment. 
(Sachs.) 


MECHANICAL  EFFECTS  OF  OSMOSE  OK  THE  PLANT. 

The  osmose  of  water  from  without  into  the  cells  of  the 
plant,  whether  occurring  on  the  root-surface,  in  the 
buds,  or  at  any  intermediate  point  where  chemical 
changes  are  going  on,  cannot  fail  to  exercise  a  great  me- 
chanical influence  on  the  phenomena  of  growth.  Boot- 
action,  for  example,  being,  as  we  have  seen,  often  suffi- 
cient to  overcome  a  considerable  hydrostatic  pressure, 
might  naturally  be  expected  to  accelerate  the  develop- 
ment of  buds  and  young  foliage,  especially  since,  as  com- 
mon observation  shows,  it  operates  in  perennial  plants, 
as  the  maple  and  grape-vine,  most  energetically  at  the 
season  when  the  issue  of  foliage  takes  place.  Experi- 
ment demonstrates  this  to  be  the  fact. 

If  a  twig  be  cut  from  a  tree  in  winter  and  be  placed  in  a 
room  having  a  summer  temperature,  the  buds,  before  dor- 


MECHANICAL  EFFECT  OF  OSMOSE  ON  PLAKTS.      407 


mant,  shortly  exhibit  signs  of  growth, 
and  if  the  cut  end  be  immersed  in  wa- 
ter, the  buds  will  enlarge  quite  after 
the  normal  manner,  as  long  as  the  nu- 
trient matters  of  the  twig  last,  or  until 
the  tissues  at  the  cut  begin  to  decay. 
It  is  the  summer  temperature  which 
excites  the  chemical  changes  that  re- 
sult in  growth.  Water  is  needful  to 
occupy  the  expanding  and  new-form- 
ing cells,  and  to  be  the  vehicle  for  the 
translocation  of  nutrient  matters  from 
the  wood  to  the  buds.  Water  enters 
the  cut  stem  by  imbibition  or  capillar- 
ity, not  merely  enough  to  replace  loss 
by  exhalation,  but  is  also  sucked  in  by 
osmose  acting  in  the  growing  cells. 
Under  the  same  conditions  as  to  tem- 
perature, the  twigs  which  are  connected 
with  active  roots  expand  earlier  and 
more  rapidly  than  cuttings.  Artificial 
pressure  on  the  water  which  is  pre- 
sented to  the  latter  acts  with  an  effect 
similar  to  that  which  the  natural  stress 
caused  by  the  root-power  exerts.  This 
fact  was  demonstrated  by  Boehm 
(Sitzungsberichte  der  Wiener  ATcad., 
1863),  in  an  experiment  which  may  be 
made  as  illustrated  by  the  cut,  Fig.  70. 
A  twig  with  buds  is  secured  by  means 
of  a  perforated  cork  into  one  end  of  a 
short,  wide  glass  tube,  which  is  closed 
below  by  another  cork  through  which 
passes  a  narrow  syphon-tube,  B.  The 
cut  end  of  the  twig  is  immersed  in 
water,  W,  which  is  put  under  pressure 
by  pouring  mercury  into  the  upper 


408  HOW  CEOPS  GBOW. 

extremity  of  the  syphon-tube.  Horse-chestnut  and  grape 
twigs  cut  in  February  and  March  and  thus  treated — the 
pressure  of  mercury  being  equal  to  six  to  eight  inches 
above  the  level,  M — after  four  to  six  weeks,  unfolded 
their  buds  with  normal  vigor,  while  twigs  similarly  cir- 
cumstanced but  without  pressure  opened  four  to  eight 
days  later  and  with  less  appearance  of  strength. 

Fr.  Schulz  (Karsten's  Bot.  Unters.,  Berlin,  II,  143) 
found  that  cuttings  of  twigs  in  the  leaf,  from  the  horse- 
chestnut,  locust,  willow  and  rose,  subjected  to  hydro- 
static pressure  in  the  same  way,  remained  longer  turges- 
cent  and  advanced  much  further  in  development  of 
leaves  and  flowers  than  twigs  simply  immersed  in  water. 

The  amount  of  water  in  the  soil  influences  both  the 
absolute  and  relative  quantity  of  this  ingredient  in  the 
plant.  It  is  a  common  observation  that  rainy  spring 
weather  causes  a  rank  growth  of  grass  and  straw,  while 
the  yield  of  hay  and  grain  is  not  correspondingly  in- 
creased. The  root-action  must  operate  with  greater 
effect,  other  things  being  equal,  in  a  nearly  saturated 
soil  than  in  one  which  is  less  moist,  and  the  young  cells 
of  a  plant  situated  in  the  former  must  be  subjected  to 
greater  internal  stress  than  those  of  one  growing  in  the 
latter — must,  as  a  consequence,  attain  greater  dimen- 
sions. It  is  not  uncommon  to  find  fleshy  roots,  espec- 
ially radishes  which  have  grown  in  hot-beds,  split  apart 
lengthwise,  and  Hallier  mentions  the  fact  of  a  sound 
root  of  petersilia  splitting  open  after  immersion  in  water 
for  two  or  three  days.  (Phytopathologie,  p.  87.)  This 
mechanical  effect  is  indeed  commonly  conjoined  with 
others  resulting  from  abundant  nutrition,  but  increased 
bulk  of  a  plant  without  corresponding  increase  of  dry 
matter  is  doubtless  in  great  part  the  consequence  of  large 
supplies  of  water  to  the  roots  and  its  vigorous  osmose 
into  the  expanding  plant. 


APPENDIX. 


COMPOSITION  OF  VARIOUS  AGRICULTURAL  PRODUCTS  giving  the  Aver- 
age  quantities  of  Water,  Nitrogen,  Ash,  and  Ash-ingredients  in 
1,000  parts  of  fresh  or  air-dry  substances.  According  to  Prof.  E. 
von  WOLFF,  1880. 


Water. 

Nitrogen. 

SO 

««! 

Potash. 

OS 

t! 

0 

do 

OJ 

§ 

3 

Magnesia. 

Phosphor- 
ic Acid. 
Sulphuric 
Acid. 

Silica. 

Chlorine. 

GRASSES. 

Rich  pasture  grass,  
Young  grass  and  after- 
math,   

782 

800 
700 
700 
700 

8GO 
820 
800 

740 

820 
S05 

•<8() 
850 
870 
)20 
815 

>:« 

71)3 
7(57 

81)0 
-iOO 
750 

8no 

100 
Mil 

»5<  ; 

140 
)33 
HI3 
888 

143 
140 
144 
HO 
143 
143 
143 
144 
145 
143 

7.2 
5.6 

5.7 
5.4 

6.0 
5.3 
4.8 

7.2 
5.3 
5.6 

1.8 
2.2 
2.1 
1.8 
1.6 
1.9 
5.4 
4.3 
2.7 
3.2 
3.4 

2.4 
3.0 
4.0 
1.6 

3.2 
4.9 
4.7 

17.6 
20.3 
16.0 

20.5 
16.0 

20.8 
16.0 
17.6 

21.1 

18.1 
17.8 
20.4 
20.5 

14.0 
14.7 
13.7 

19.2 
8.6 
14.3 

9.1 
8.2 
7.5 
6.4 
7.1 
4.9 
10.0 
19.7 
7.4 
9.8 
9.5 

15.6 
9.6 
8.0 
5.8 
8.1 
5.0 
16.0 
10.0 

26.7 
29.5 
12.4 
16.0 
18.3 
22.3 
18.0 
16.8 
17.0 
17.9 

8.1 

5.3 
5.9 
7.1 
7.1 

5.1 
5.5 
4.4 

4.5 
2.4 
3.1 

4.8 
3.0 
3.5 
2.9 
3.8 
1.6 
5.4 
7.7 
2.5 
4.7 
5.8 

5.8 
4.3 
3.6 
2.4 
3.7 
1.2. 
2.7 
5.1 

4.8 
3.3 
3.7 
3.3 

5.6 
4.7 
6.2 
5.2 
2.8 
5.8 

0.3 

0.7 
0.8 
0.7 
0.4 

0.3 
0.3 
0.3 

0.3 
0.3 
1.0 

1.5 

1.7 
0.4 
0.6 
0.6 

1.0 
0.2 

0.4 
0.2 

1.0 
0.3 

1.5 
0.8 
0.5 
0.6 
0.8 
0.9 
5.7 
0.2 

0.4 
0.4 
0.1 
0.5 
0.3 
0.5 
0.3 
0.3 
0.7 
0.3 

2.6 

2.5 
1.1 
1.5 
1.7 

3.9 
4.5 
4.8 

8.5 

2.9 
4.3 

0.3 
0.9 
0.9 
0.7 
0.4 
0.7 
1.1 
2.0 
1.6 
0.3 
0.3 

2.8 
1.2 
0.5 
0.4 
0.5 
0.6 
1.9 
0.1 

1.0 

0.2 
0.3 
0.2 
0.5 
0.6 

0.5 
0.1 
0.5 

1.2 

1.2 
0.5 
0.4 
0.7 

1.3 
1.6 
1.5 

0.9 
1.1 
1.4 

0.4 
0.4 
0.3 
0.2' 
0.6 
0.2 
0.6 
0.4 
0.3 
0.3 
0.5 

0.6 
0.4 
0.3 
0.2 
0.2 
0.2 
1.0 
0.3 

1.9 
2.8 
1.9 
2.4 
2.2 
2.0 
2.2 
2.0 
2.1 
2.0 

1.9 

1.4 
1.3 

2.2 
2.4 

1.7 
1.5 
1.3 

1.6 
0.9 
1.8 

0.8 
1.1 
1.1 
0.8 
0.9 
0.5 
1.9 
2.0 
1.3 
1.4 
1.6 

1.4 
1.1 
1.6 
1.2 
0.7 
0.9 
1.6 
3.4 

6.8 
6.5 
5.7 
8.1 
9.0 
7.8 
9.2 
7.9 
5.6 
8.5 

0.7 

1.0 

0.5 
0.8 
0.6 

0.3 
0.4 
0.4 

1.1 
0.4 
1.1 

0.3 
0.5 
0.7 
0.7 
0.3 
0.3 
0.5 
4.9 
0.4 
0.6 
0.6 

2.4 
1.3 
1.0 
0.4 
0.3 
0.3 
1.1 
0.4 

0.5 
0.1 
0.1 

0.2 
0.4 

0.1 

0.5 
0.2 

4.1 

4.6 
5.9 
6.5 
6.6 

0.4 
0.4 
0.4 

1.8 
0.3 
0.6 

0.2 
0.2 
0.1 
0.1 
0.2 

0.2 
1.5 

0.7 
0.2 
0.2 

0.1 
0.1 
0.3 
0.5 
1.3 
05 
0.7 
0.1 

10.5 
15.6 
0.3 
1.2 
0.3 
5.8 
0.2 
0.3 
4.9 
0,3  1 

2.1 

1.1 
1.3 
2.1 
1.1 

0.6 
0.5 
0.5 

0.6 
0.5 
0.6 

0.9 
0.4 
0.5 
0.3 
0.3 
0.5 
0.4 
0.3 
0.2 
0.4 
0.3 

1.3 

0.5 
0.3 
0.4 
0.4 
0.3 
1.0 
0.1 

0.3 
0.1 
0.2 

0.1 

0.2 

0.1 
0,1 

Orchard  grass,  

Rye  grass,  

Timothy,  

CLOVERS  AND  LEGUMES. 

Red  clover,  young,  
Red  clover  in  bud,  
Red  clover  in  flower,  .  .  . 
Lucern    or    Alfalfa,    in 
early  bloom,  

Alsike  clover,  

White  clover  in  flower, 

ROOTS,  TUBERS,  BULBS. 

Beets,  

Carrots,  

Rutabagas,  

Turnips,  

Sugar-beets,  

Radish,  

Parsnip,  

Horseradish,  

Onion  

Artichoke,  Helianthus,  . 
Potato,  

"VEGETABLES." 

Cabbage,  loose  outer 
leaves,  

Cabbage,  heart,  
Cauliflower,  heart,  
Cucumber,  fruit,  
Lettuce,  

Asparagus,  sprouts,  
Spinage,  

Mushrooms,  edible,  

SEEDS  OF   CEREALS. 

Oats,  

Millet,  
Maize,  

Sorghum,  

Spring  Wheat,  
Spring  Barley,  
Spring  Rve,  

Winter  Wheat,  
Winter  Barley,  
Winter  live,  

409 


410 


HOW  CROPS  GKOTV. 


COMPOSITION  OF  VARIOUS  AGRICULTURAL  PRODUCTS.— [Continued.] 


Water. 

Nitrogen. 

en 
^ 

Potash. 

A 

- 
5 

00 

Lime. 

Magnesia. 

Phosphor- 
Acid. 

« 

•cd 

P 

O3 

Silica. 

Chlorine.  1 

SEEDS  OF  LEGUMES  AND 
CLOVERS. 

Horse  bean,  Vicia,  
Garden  bean,  Phaseolus, 

145 
150 
100 
143 
150 
150 

77 
122 

us 
i:;o 

K\\ 
S31 

SL>5 

s;is 
830 

150 
150 

160 

150 
14.'! 
167 
165 
160 
15(1 
165 
160 

160 

143 
143 
150 
143 
143 
143 
160 
160 

143 
113 
143 
140 

ISO 
ISO 
120 
10S 
140 
112 
I'".' 

40.8 
39.0 
53.4 
35.8 
30.5 

36.5 
26.1 
32.8 

0.6 

0.6 

1.7 

18.5 
25.5 

19.1 

16.3 

35.5 
24.5 
19.7 
12.5 
23.2 
24.0 

23.0 

5.6 
6.4 
4.8 
5.6 
4.8 
4.0 
13.0 
10.4 

6.4 
5.8 
7.2 
2.3 

34.8 
24.6 

25.0 
62.1 

47.2 

31.0 
27.4 
28.3 
23.4 
38.3 
33.8 

33.8 
46.3 
32.6 
36.5 

2.2 
3.3 
3.9 
2.9 
8.8 

29.7 
82.4 

76.0 

59.4 
58.2 
82.3 
68.4 
57.6 
44.7 
61.1 
40.0 

62.0 

61.6 
45.9 
45.3 
38.1 
46.0 
38.2 
51.7 
43.1 

71.2 

82.7 
92.0 
4.5 

140.7 
64.7 
31.1 
31.7 
72.9 
66.4 
51.3 

12.9 
12.1 
12.6 
10.1 
13.5 
12.3 

10.9 
9.4 
10.0 
5.9 

0.8 
1.8 
2.0 
1.7 
5.0 

7.7 
31.6 

22.3 

19.3 

20.2 
29.7 
25.3 
18.6 
10.0 
13.1 
11.1 

14.6 

16.3 
10.7 
16.4 
11.0 
6.3 
8.6 
24.2 
9.9 

4.5 
5.2 
8.4 
2.3 

40.9 
2H.2 
9.7 
5.5 
17.9 
15.8 
12.5 

0.3 
0.1 
0.3 

0.2 

0.4 

0.2 
2.3 

0.4 
0.7 
2.0 

0.6 
0.3 
0.1 

0.1 
0.4 

1.3 
3.0 

1.0 

2.0 
1.9 

1.4 
1.1 
1.4 
4,1 
1.1' 

1.1 
2.0 

1.6 
0.5 
1.0 

0.6 

0.7 
1.1 

1.8 

2.9 
0.3 

1.7 

0.1 

4.5 

6.6 

2.5 
0.6 
1.9 

o.s 

1.5 
1.5 
1.7 
1.1 

2.5 
2.5 

1.9 
10.9 
2.6 
7.0 

0.1 
0.3 
0.3 
0.3 
1.0 

7.1 
10.1 

10.4 

3.4 

4.3 
23.5 
20.7 
20.1 
15.8 
18.4 
13.6 

25.2 

4.3 
3.3 
4.9 
2.6 
2.7 
3.1 
9.5 
15.9 

4.0 
3.5 
1.7 
0.2 

50.7 
12.4 
6.9 
16.8 
19.7 
2.9 
4.3 

2.2 
2.1 
2.5 
1.9 
4.9 
3.9 

5.6 
2.6 
4.7 
3.7 

0.2 
0.2 
0.2 
0.2 
0.4 

2.4 
4.6 

5.1 

1.7 
1.3 

7.6 

6.3 
6.9 
5.8 
5.0 

3.1 

?:i 

2.6 
0.9 
1.1 
1.2 
1.9 
3.5 

1.5 
1.1 
1.2 
0.2 

10.4 
0.5 
2.0 
2.1 
7.0 
10.1 
8.1 

12.1 

9.7 
10.4 
8.4 
14.5 
11.6 

10.5 
16.9 
13.5 
14.6 

0.3 
0.5 
0.6 
0.4 
1.4 

2.7 
7.4 

5.9 

5.6 
6.2 
10.0 
6.9 
5.6 
4.4 
7.8 
4.1 

5.3 

2.8 
1.9 
3.8 
2.0 
2.2 
2.5 
6.1 
3.5 

1.3 
5.6 
4.0 
0.2 

6.6 
9.2 
4.2 
2.1 
5.8 
30.5 
16.2 

1.1 
1.1 

0.8 
0.8 
0.9 
1.6 

0.7 
0.1 
0.8 
1.8 

0.1 

0.2 
0.2 
0.1 
0.5 

1.4 
2.7 

4.1 

1.5 
2.3 
1.8 
1.7 
1.9 
1.4 
4.5 
1.6 

3.6 

2.0 
1.8 
2.4 
1.2 
1.1 
1.6 
2.7 
2.7 

3.5 
0.1 

e.i 

8.5 
2.2 
2.0 
0.6 
2.9 
0.8 
1.7 

0.2 
0.2 

0.2 
0.5 
0.8 

0.1 
5.5 
0.4 
0.9 

0.1 

0.1 
0.4 
0.1 
0.3 

7.2 
15.9 

19.4 

24.7 
18.5 
2.5 
1.8 
1.6 
3.0 
2.7 
1.6 

5.9 

28.8 
23.4 
13.1 
18.2 
31.0 
18.8 
2.9 
2.9 

50.4 
66.4 
74.7 
1.3 

8.1 
1.6 
1.7 
3.1 
13.3 
5.5 
6.4 

0.5 
0.3 
0.1 
0.4 
0.5 
0.5 

0.5 
0.2 

0.1 
0.1 

0.7 
8.4 

4.5 

2.3 
6.1 
3.3 

2.4 
2.2 
1.3 
2.6 
2.2 

1.9 

2.7 
1.5 
0.6 
0.8 
0.8 
0.8 
4.1 
2.3 

0.8 
0.4 

0.2 

9.4 
2.4 
1.3 
0.6 
3.7 

0.4 

Pea       

Red  Clover,  

White  Clover       

OIL  SEEDS. 

Cotton        

Flax         

FRUITS. 

Apple,  entire  fruit,  
Pear,  entire  fruit,  
Cherry,  entire  fruit,  — 
Plum  entire  fruit,  

Grape,  entire  fruit,  

HAY. 

Alpine  hay,  

From  very  young  grass, 
From  young  grass  and 
aftermath,  

From    cereals    cut    in 

English  rye  grass,  
Red  Clover,  young,  .... 
Red  Clover  in  bud,..  .. 
Red  Clover  in  flower  .. 
Red  Clover,  ripe,  
White  Clover  in  flower, 
Alsike  Clover,  

Lucern   (Alfalfa)    early 

STRAW. 

Oat  \  

Barley,  
Maize,  

Spring  Wheat,  

Winter  Wheat,  

Winter  Rye,  

Buckwheat,  

Pea,  

CHAFF,  ETC. 

Oat  Chaff,  

Rye  Chaff,  

Wheat  Chaff     

MISCELLANEOUS. 

Tobacco  leaves,  
Tobacco  stems,  
Flax  stalks,  

Hops,  entire  plant,  

INDEX. 


Absorption  by  the  root,  260, 269,  272 
Access  of  air  to  Interior  of 

Plant, 313 

Aestic  Acid 76 

Acetamide, 115 

Acids,  Definition  of    .....  81 

Acids,  Test  for 82 

Acid  elements 127 

Acid-proteids, 99 

Adhesion, 9,388 

Agriculture,  Art  of 1 

Agricultural  products,  Compo- 

sition'in  1,000  parts,  ...  409 
Agricultural  Science,  Scope  of  .  7 
Air-passages  in  plant,  ....  313 

Air-roots, 273 

Akene, 331 

Albumin, 89 

Albuminates, 99 

Albuminoids,    Characters   and 

composition,    ...  87,  104, 106 
Albuminoids  in  animal  nutrit- 
ion,     108 

Albuminoids,  Diffusion  of  .  .  .403 
Albuminoids  in  oat-plant,  .  .  234 
Albuminoids,  Mutual  relations 

of 107 

Albuminoids,  Proportion  of,  in 
vegetable  products,    .    .    .  114 

Albumose 101 

Alburnum, 305 

Aleurone, 110 

Alkali-earths 81,  139 

Alkali-earths,  Metals  of     .    .    .139 

Alkali-metals 138 

Alkalies, 81,138 

Alkali-proteids, 99 

Alkaloids, 120 

Allylsulphocyanate, 129 

Alumina, 143 

Aluminium, 143 

Aluminium  phosphate 28 

Amides, 114,118 

Amido-acids, 114, 118 

Amidoacetic  acid, 115 

Amidocaproic  acid, 116 

Amid*  (valeric  acid,     ....    .116 

Amidulin 52 

Amines, .119 

Ammonium  Carbonate,  ...  33 
Ammonium  Salts  In  plant,  82, 113 
A  my  Luii,.  ..'...,,,  62 

411 


Amyloid, 43 

Amylodextrin, 63 

Amyloses, 39,  40 

Anhydrous  phosphoric  acid,  .  132 
Anhydrous  sulphuric  acid,  .  .130 

Anther, 318 

Apatite, 148 

Arabic  acid, 58 

Arabin, 58 

Arabinose, 65 

Arrow  root, 48 

Arsenic  in  plants,  .  .  .  137, 210 
Ash-ingredients,  ....  126, 161 
Ash-ingredients,  Excess  of  .  .201 
Ash-ingredients,  Excess  of,  how 

disposed  of 203 

Ash-ingredients,  Function  of  in 

plant, 210 

Ash-ingredients,  State  of,  in 

plant, 207 

Ash  of  plants '  13, 126 

Ash  of  plants,  Analyses,  Tables 

of 164 

Ash  of  plants,  Composition  of, 

normal, 177 

Ash  of  plants,  Composition  of, 

variations  in 151 

Ash,  Proportions  of,  Tables,  .  .152 

Asparagin, 116 

Assimilation, 364 

Atmosphere,  Offices  of .  .  .  .367 

Atoms, ..30 

Atomic  weight, 31 

Avenin 120 

Bark, 291,  207 

Barium  in  plants, 210 

Bases,  Definition  of 81 

Bast-cells,  Bast-tissue,  293,  295,  297 
Bean,  Leaf,  Section  of  ...  .308 

Bean,  Seed 334 

Berry, 331 

Betaln 116 

Biology, 10 

Bleeding  of  vine,  ....  271,371 

Blood-fibrin, 91 

Bone-black, 15 

Boron,  Boric  acid, 210 

Buds,  Structure  of 283 

Buds,  Development  under  pres- 
sure,   406 

Bulbs, .289 

Butyric  acid,  ........  70 


412 


CROPS  GROW. 


Caesium,  Action  on  oat,    .    .    .209 

Caffein, 117 

Calcium, 139,  214 

Calcium,  carbonate, 145 

Calcium,  hydroxide,     ....  143 

Calcium,  oxide, 139 

Calcium,  phosphate,     .    .    .28, 148 

Calcium,  sulphate 146 

Callous, 382 

Calyx 317 

Cambium, 294,  295,  299 

Cane-sugar, 65 

Capillary  attraction,     ....  389 

Carbamide, 115 

Carbhydrates, 39 

Carbhydrates,  Composition  .  .  72 
Carbhydrates,  Transformations 

of .  70 

Carbon,  Properties  of    ....    14 

Carbon  in  ash, 128 

Carbon  dioxide, 128 

Carbonates, 128,  144 

Carbonate  of  lime, 145 

Carbonate  of  potash, 144 

Carbonate  of  soda, 144 

Carbonic  acid, 19, 128 

Carbonic  acid  as  food  of  plant,  328 
Carbonic  acid  in  ash-analyses,  149 

Carboxyl, 75,  77 

Casein, 84 

Caseose 101 

Cassava, 51 

Causes  of  motion  of  juices,    .    .385 

Cell-contents, 249 

Cell-multiplication, 252 

Cell,  Structure  of  .    .    .    .    .    .245 

Cells,  Forms  of 247 

Cellular  plants, 243 

Cellular  tissue, 255 

Cellulose, 40 

Cellulose,  Composition  ....  44 
Cellulose,  Estimation  ....  45 

Cellulose  nitrates, 43 

Cullulose  sulphates, 43 

Cellulose,  Test  for 44 

Cellulose,  Quantity  of,  in  plants,  46 

Chemical  affinity, 29 

Chemical  affinity  overcome  by 

osmose, 403 

Chemical  combination,  ...  29 
Chemical  decomposition,  ...  30 

Chemistry, 10 

Chlorides 133, 149 

Chloride  of  ammonium,  decom- 
posed by  plant 184 

Chlorine, 132 

Chlorine  essential  to  crops  ?  .  .194 
Chlorine,  function  in  plant,  .  218 
Chlorine  in  strand  plants,  .  .191 

Chlorophyl, 124,  307,  308 

Chlorophyl  requires  iron,     .    .  220 

Chlorophyllan, 125 

Choline, 119 

Circulation  of  sap, 369 

Citric  acid, 80 

Citrates, 80, 149 

Classes  of  plants, 329 

Classification  botanical,    .   .   .329 


Clover,  washed  by  rain,    .    .    .  204 

Colloids, 392 

Con-''utin, 95,97 

Combustion, 18 

Composite  plants, 330 

Concentration  of  plant-food,     .185 
Concretions  in  plant,    ....  205 

Coniferous  plants, 330 

Copper  in  plants,  ......  210 

Cork, 298 

Corm, .  288 

Corolla 317 

Cotyledon, .290, 333 

Coniferous  plants,  .....    .330 

Cryptogams, 315,  329 

Crystalloid  aleurone,     .    .    .    .111 

Crystalloids, 392 

Crystals  in  plant, 206 

Culms, 284 

Cyanides, 127, 129 

Cyanogen, 129 

Definite  proportions,  Law  of .    .30 

Density  of  seeds, 339 

Depth  of  sowing,     ......    .355 

Dextrin, 53 

Dextrose, 63 

Diastase,     ......  67, 103,  360 

Diffusion  of  liquids, 390 

Dioecious  plants, 318 

Drains  stopped  by  roots,    .    .    .276 

Drupe, 331 

Dry   weather,    Effect    of,  on 

plants 157 

Ducts, 255,294 

Dulcite, 74 

Dundonald's  treatise  on  Agri- 
cultural Chemistry,    ...     4 

Elements  of  Matter, 8 

Embryo, 333 

Endogens, 259,  290,  334 

Endosmose, 394 

Endosperm, 332 

Enzymes, 103 

Epidermis,  ........    .291 

Epidermis  of  leaf, 308 

Eremacausis, „    .  20 

Excretions  from  roots,  ....  280 
Exhalation  of  water  from  foli- 
age,     309 

Exogens,    ....    239,  293,  296,  334 

Exosmose, 394 

Exudation  of  ash-ingredients,  203 

Eyes  of  potato, „    .  28£ 

Families, 328 

Fatty  acids, 75 

Fats, 83 

Fats  converted  into  starch, .    .  358 

Fat  in  oat  crop, 230 

Fat  in  Vegetable  Products,  .    .    87 
Ferments,     ........    .102 

Ferric  oxide, ........  142 

Ferric  hydroxide, 142 

Ferric  salts, 142 

Ferrous  oxide,     ......    .141 

Ferrous  hydroxide,  .....  141 

Ferrous  salts,  .......    .142 

Fertilization, .319 

Fibrin,     .,,.,.,.    .91,9* 


INDEX. 


413 


Flbrinogen, .„    91,  96 

Flax  fiber,  Fig.,  ....  'L., 41,  248 
Flax  seed  mucilage,     .    .    .    58,  62 

Flesh  fibrin, 92 

Flower, 317 

Flow  of  sap, 371 

Fluorine  in  plants, 209 

Foliage,  Offices  of 314 

Food  of  Plant, 366 

Formative  layer, 245 

Formulas,  Chemical,     .    .    .  33,  73 

Fructification, 319 

Fructose, 63 

Fruit, 330 

Galactin, 61 

Galactose, 65 

Gases,  how  distributed  through- 
out the  plant, 404 

Gelatinous  Silica, 136 

Genus  ;  Genera, 328 

Germ, 333 

Germination, 349 

Germination,  Conditions  of  .    .  351 
Germination,  Chemical  Physi- 
ology of 357 

Girdling, 383 

Glauber's  Salt, 146 

Gliadin, 92 

Globulin, 96 

Glucoses, 39,  63 

Glucosides, 69 

Glutamin 116 

Gluten, 92 

Gluten-Casein, 93,  95 

Glycerin, 86 

Glycogen 56 

Glyco^oll, 116 

Glycollic  acid, 77 

Gourd  fruits 331 

Grains, 331 

Grape  Sugar, 63 

Growth, 252 

Growtli  of  roots, 256 

Gum,  Amount  of,  in  plants,  .    .  62 

Gum  Arabic, 57 

Gum  Tragacanth, 57 

Gun  Cotton 43 

Gypsum 147 

Haemetin, 110 

Haemoglobin, 109 

Hallett's  pedigree  wheat,    .158,  344 

Hybrid,  Hybrfdizing, 324 

Hydration  of  membranes,    .    .  396 
Hydrochloric  acid, ....    23,  133 

Hydrocyanic  acid, 129 

Hydrogen, 22, 112 

Hydrogen  chloride, 23 

Hydrogen  sulphide,    ...    26,  129 

Imbibition 386 

Imides, 117 

Inorganic  matter, 12 

Internodes, 284 

Inniiii. 55 

Invertin, 103 

Iodine  in  plants,    ....    134,  210 

Iodine,  Solution  of 44 

Iron 141,192 

Iron,  Function  pf    .   ,   ,   .   .    .2.J9 


Isomerism, 73 

Juices  of  the  Plant, 369 

Lactic  Acid, 77 

Lactose, 68 

Latent  buds, 285 

Latex, 304 

Layers, 286 

Lead  in  plants, 210 

Leaf  pores 309 

Leaves,  Structure  of    ...  306,  308 
Leaves,  office  in  nutrition,    .    .  328 

Lecithin, 122 

Legume, 332 

Legumin, .    .*  95 

Leguminous  plants, 332 

Leucin, 116 

Levulin, 56 

Levulose, 63 

Lignin, 41 

Lime, 139 

Liquid  Diffusion, 390 

Lithia,  Lithium,  in  plants,    .    .209 
Lupanin,  Lupinin,  Lupinidin,    120 

Magnesia, 140 

Magnesium, 140,  215 

Magnesium  hydroxide 141 

Magnesium  oxide, 140 

Maize  fibrin, 93 

Malates, 149 

Malic  acid, 79 

Malonic  acid, 79 

Malt,  Chemistry  of 358 

Maltose, 67 

Manganese, 142, 193 

Mannite, 74 

Mannose, . 65 

Margarin, 85 

Medullary  rays, 299 

Membrane-diffusion,     .    .    393, 397 
Membranes,    Influence  on  mo- 
tion of  juices, 404 

Metals,  Metallic  elements,     .    .138 

Metapectic  acid, 59 

Metarabin, 59 

Milk  ducts, 304 

Miik  Sugar 68 

Molecules,  Molecular  Weights,    32 

Monaecious  plants, 319 

Motion  caused  by  adhesion,  .    .389 

Mucedin, 92,  321 

Multiple  Proportions,     ....  32 

Muriate  of  potash, 149 

Muriatic  acid, 133 

Myosin, 97,  98 

Nectar,  Nectaries 319 

Neurin, 120 

Nicotin, •".    .120 

Niter,  Nitrate  of  potassium, .    .  149 
Nitrates  in  plants,  ....  113, 149 

Nitric  Acid  in  plant, 113 

Nitrogen,  Properties  of  .    .    .    .20 

Nitrogen  in  ash, 127 

Nodes, 284 

Non-metals, 127 

Notation,  Chemical    .    .    .....    .33 

Nuclein, 122 

Nucleus 300 

Nut,     ,   ,    .    »    »    »    .    »    t    .   ,331 


414 


HOW  CROPS  GROW. 


Nutrient  matters  In  plant,  Mo- 
tion of  401 

Nutrition  of  seedling 357 

Nutrition  of  plant, 366 

Oat    plant,    Composition    and 

growth  of 223 

Oats,  weight  per  bushel,    .    .    .176 

Oil  in  seeds,  etc., 83 

Oil  of  vitriol, 26,  130 

Oils,  Properties  of 83 

Oleic  acid 86 

Olein, 85 

Orders, 328 

Organic  matter, 12 

Organism,  Organs 243 

Osmose, 393 

Osmose,  mechanical  effects  on 

plant, 406 

Osmometer, 394 

Ovaries 318 

Ovules, 318 

Oxalates 78,  149 

Oxalic  acid, 78 

Oxides, 19,  20 

Oxides  of  iron,  described, .  19, 141 
Oxides  of  manganese,  described  142 

Oxyfatty  acids, 77 

Oxygen,  Properties  of  ....  16 
Oxygen  occurrence  in  ash,  .  .128 
Oxygen  in  Assimilation,  .  .  .  364 
Oxygen  in  Germination,  .  .  .353 

Palmitic  acid, 86 

Palmitin, 85 

Papain 104 

Parenchyma, 255 

Papilionaceous  plants,     .    .    .  330 

Pappus, 331 

Pararabin, 59 

Paraglobulin, 96,  99 

Paragalactin, 61 

Pectic  acid, 74 

Pectin  bodies, 58,  59,  74 

Pectosic  acid, 74 

Pectose, 58,  61,  74 

Pedigree  wheat, 158,  344 

Pepsin, 104 

Peptones 100 

Permeability  of  cells,  ....  253 

Petals, 318 

Phanerogams,  Phaenogams,316, 329 

Phloridzin, 69 

Phosphate  of  lime, 148 

Phosphate  of  soda, 148 

Phosphate  of  potash,    ....  147 

Phosphates, 28,  132,  147 

Phosphates  function  in  plants,  211 
Phosphates   relation    to    albu- 
minoids,      221 

Phosphoric  acid, 27, 132 

Phosphorite, 148 

Phosphorized  substances,    .    .  122 

Phosphorus, 27 

Phosphorus  pentoxide,     .    .  27, 132 

Physics, 10 

Physiology, 10 

Piperin, 121 

Pistils 318 

nt  u,    ,.,,,,,,..  .aw: 


Pith  rays, 299 

Plastic  Elements  of  Nutrition,  109 

Plumule, 333 

Pollarding, 286 

Pollen, 318 

Polygonum  convolvulus,  Fertil- 
ization of,  Fig., 295 

Pome, 331 

Porosity  of  vegetable  tissues,    .385 
Potato  leaf,  Pores  of,  Fig.,    .    .  309 
Potato  stem,  Section  of,  Fig.,     .304 
Potato  tuber,  Structure  and  Sec- 
tion of,  Fig., 300 

Potash, 138, 144 

Potash  lye 139 

Potassium, 138,211 

Potassium  carbonate,   .   .   .   J44 
Potassium  Chloride, .....  149 

Potassium  hydroxide,    ...    .139 

Potassium  oxide, ......  138 

Potassium  phosphate,    ...    .147 

Potassium  silicate,    .....  134 

Potassium  sulphate,   ....    .146 

Prosenchyma,    .......  255 

Protagon,     ........    .123 

Proteoses, 100 

Protoplasm, .245 

Protein  bodies,  or  Proteids, .    .    87 
Proximate  Principles,    ....  37 

Quack  grass,  ........  287 

Quantitative   relations   among 

ingredients  of  plant,  .    .    .  220 
Quartz, .134 


Quince  seed  mucilage, ....  62 

Radicle, 333 

Rafflnose, 68 

Reproductive  Organs,  .  .  243,  315 

Rhizome, 287 

Rind, 297 

Rock  Crystal, 134 

Root-action,  imitated,  .  .  .  .400 
Root-action,  Osmose  in  ...  399 

Root  cap, .257 

Root  distinguished  from  stem,  258 

Root  excretions 280 

Root  hairs, 265 

Root,  Seat  of  absorptive  force 

In, 270,399 

Root  stock, 287 

Rootlets, 260 

Roots,  Growth  of 256 

Roots  contact  with  soil,  .  .  .  2ftf 
Roots  going  down  for  water, .  .276 
Roots,  Search  of  food  by  .  .  .263 

Roots,  Quantity  of 263 

Rubidium  action  on  oat,  .  .  .209 

Rxinners,  , 286 

Saccharose, 60 

Saccharose,  Amount  of,  in 

plants 66 

Sago, -51 

Salicin, 69 


Salicornia, 191 

Sal-soda, 145 

Sal  sola, 191 

Salts,  Definition  of 81 

Salts,  in  ash  of  plants,   .    .    .    .143 
Saltwort,    .........  m 


INDEX. 


415 


Samphire,    . 191 

Sap, 369 

Sap,  Acid  and  alkaline  .    .    .    .378 

Sap  ascending, 379,  384 

Sap  descending, 382 

Sap,  Composition  of 376 

Sap  of  sunflower, 378 

Sap,  Spring  flow  of    .    .    .    ,    .  370 

Sap  wood, .305 

Saponification, 85 

Saxifraya  crustata, 206 

Seed, 332 

Seed  vessel, 330 

Seed,  Ancestry  of 346 

Seeds,  constancy  of  composition!45 

Seeds,  Density  of 339 

Seeds,  Weight  of 340 

Seeds,  Water  imbibed  by .    .    .399 
Selective  power  of  plant,  .    .    .401 

Seminose, 65 

Sepals, 317 

Sieve-cells, 303 

Sieve-cells  In  pith, .    .    .    .  343,  345 

Silica, 134 

Silica  entrance  into  plant,     .    .402 
Silica,  Function  of,  in  plant,    .  216 

Silica  in  ash, 197 

Silica  in  textile  materials,  .    .  200 
Silica  unessential  to  plants, .    .197 

Silicates, 134 

Silicate  of  potassium,    ...    .134 

Silicic  acids, 135 

Silicon, 134 

Silicon,  Dioxide 134 

Silk  of  maize, 319 

Silver-grain 299 

Sinapin, 120 

Soaps, 93 

Sodium, 139 

Sodium  carbonate, 144 

Sodium  essential  to  ag.  plants?  186 

Sodium  hydroxide, 139 

Sodium  in  strand  and  marine 

plants, •    .191 

Sodium  oxide, 139 

Sodium  sulphate, 146 

Sodium,  Variations  of,  in  field- 
crops,    188 

Sodium  Chloride 149 

Soil.  Offices  of 368 

Solanin, 121 

Solution  of  starch  in  Germina- 
tion,     358,  361 

Soluble  silica, 135 

Soluble  starch, 52 

Species, 326 

Spirits  of  salt, 133 

Spongioles, 257 

Spores, 316 

Sports, 327 

Stamens, 318 

Starch,  amount  in  plants,    .    .    51 

Starch-cellulose, 50 

Starch  estimation, 52 

Starch  in  wood, 373,  376 

Starch,  Properties  of    ....    47 

Starch,  Test  for 49 

Stearicacid, 86 


Stearin,    ..........  Kr> 

Stem,  Endogenous     .....  290 

Stem,  Exogenous 296 

Stem,  Structure  of 289 

Stems, 282 

Stigma, 318 

Stomata, .309 

Stool, 287 

Suckers, 287 

Sucroses, 39, 65 

Sugar,  Estimation  of  .    .    .    .    .66 

Sugar,  in  cereals, 69 

Sugar  in  Sap, .377 

Sugar  of  milk, 68 

Sulphate  of  lime, 146 

Sulphate  of  potash 146 

Sulphate  of  soda 146 

Sulphates, 26, 131, 146 

Sulphates,  Function  of  ...  .210 
Sulphates  reduced  by  plant,  .  208 

Sulphides, .26,  130 

Sulphide  of  potassium,  ...    .130 

Sulphites, 129 

Sulphur, 25, 129 

Sulphur  in  oat, 208 

Sulphur  dioxide, 25, 130 

Sulphureted  hydrogen,     .    .26, 115 

Sulphurets 26 

Sulphuric   acid, 26, 130 

Sulphuric  acid  in  oat,  ...  .208 
Sulphuric  oxide  (SOS),  ....  209 
Sulphur  trioxide  (SOg),  .  .  .25,130 

Sulphurous  acid, 25, 129 

Symbols,  Chemical     .....  31 

Tao-foo 96 

Tapioca,   ..........51 

Tap-roots, 259 

Tartaric  acid, 80 

Tartrates, 80 

Tassels  of  maize,    .....    .319 

Theobromin, 118 

Tillering, .287 

Titanic  acid 137 

Titanium, 137,  209 

Translocation  of  substances  In 

plant, 237 

Trypsin, 104 

Tubers, .273,  288 

Tuscan  hat-wheat,    .....  158 

Tyrosin, 116 

Ultimate  Composition  of  Vege- 
table Matters, 13,  29 

Umbelliferous  plants,  ....  330  ' 
Unripe  seed,  Plants  from  .  .  .338 

Urea, 115 

Valence, 35 

Varieties, 158,326,327 

Vascular  bundle  of  maize 

stalk, 291,293 

Vascular-tissue, 255 

Vegetable  acids,    ......    75 

Vegetable  albumin,    .....  90 

Vegetable  casein 94 

Vegetable  cell,    ......    .243 

Vegetable  fibrin, 92 

Vegetable  globulins, 97 

Vegetable  mucilage,.  ....  57 
Vegetable  myosina, 98 


416 


HOW  CROPS  GROW. 


Vegetable  parchment,  ....    44 

Vegetable  tissue, 246 

Vegetative  organs 243 

Vernin, 118 

Vicin, 120 

Vitality  of  roots, 282 

Vitality  of  seeds 335 

Vitellin, 96 

"Water,  Composition  of  ....  37 
Water,  Estimation  of  ....  39 
Water,  Formation  of  ....  24 
"Water  in  air-dry  plants  ....  39 
Water  in  fresh  plants,  ....  38 
Water  in  vegetation,  Free  ...  39 
Water  in  vegetation,  Hygro- 
scopic,  39 


"Water-oven, 88 

Water-culture, 181 

Water-glass, 135 

Water  Boots, 273 

Wax, 83 

Wood, 41,305 

Wood  cells 293 

Wood  cells  of  conifers,  .    .    .    .301 

Woody  stems, 305 

Woody  tissue, 255 

Xylin, 61 

Xylose, 62 

Yeast 103 

Zanthophyl, 125 

Zein, 93 

Zinc M<t 


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The  Book  of  Alfalfa 

History,  Cultivation  and  Merits.  Its  Uses  as  a  Forage 
and  Fertilizer.  The  appearance  of  the  Hon.  F.  D.  COBURN'S 
little  book  on  Alfalfa  a  few  years  ago  has  been  a  profit  revela- 
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Clean  Milk 

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Bean  Culture 

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Celery  Culture 

By  W.  R.  BEATTIE.  A  practical  guide  for  beginners  and  a 
standard  reference  of  great  interest  to  persons  already  engaged 
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and  marketing  of  celery  in  carload  lots.  Fully  illustrated. 
150  pages.  5x7  inches.  Cloth $0.50 

Tomato  Culture 

By  WILL  W.  TRACY.  The  author  has  rounded  up  in  this 
book  the  most  complete  account  of  tomato  culture  in  all  its 
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No  gardener  or  farmer  can  afford  to  be  without  the  book. 
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reader  has  here  suggestions  and  information  nowhere  else 
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The  Potato 

By  SAMUEL  FRASER.  This  book  is  destined  to  rank  as  a 
standard  work  upon  Potato  Culture.  While  the  practical  side 
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and  authoritative  book  on  the  potato  ever  published  in  America. 
Illustrated.  200  pages.  5x7  inches.  Cloth $0.75 

Dwarf  Fruit  Trees 

By  F.  A.  WAUGH.  This  interesting  book  describes  in  detail 
the  several  varieties  of  dwarf  fruit  trees,  their  propagation, 
planting,  pruning,  care  and  general  management.  Where  there 
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Cloth.  .  ...  r*  r  *  *  r  •••....  $0.50 


Cabbage,  Cauliflower  and  Allied  Vegetables 

By  C.  L.  ALLEN.  A  practical  treatise  on  the  various 
types  and  varieties  of  cabbage,  cauliflower,  broccoli,  Brussels 
sprouts,  kale,  collards  and  kohl-rabi.  An  explanation  is  given 
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management  pertaining  to  the  entire  cabbage  group.  After  this 
each  class  is  treated  separately  and  in  detail.  The  chapter 
on  seed  raising  is  probably  the  most  authoritative  treatise  on 
this  subject  ever  published.  Insects  and  fungi  attacking  this 
class  of  vegetables  are  given  due  attention.  Illustrated.  126 
pages.  5x7  inches.  Cloth.  ......  $0.50 


Asparagus 

By  F.  M.  HEXAMER.  This  is  the  first  book  published  in 
America  which  is  exclusively  devoted  to  the  raismg  of  aspara- 
gus for  home  use  as  well  as  for  market.  It  is  a  practical 
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given  to  the  importance  of  asparagus  as  a  farm  and  money 
crop.  Illustrated.  174  pages.  5x7  inches.  Cloth.  -  $0.50 


The  New  Onion  Culture 

By  T.  GREINER.  Rewritten,  greatly  enlarged  and  brought 
up  to  date.  A  new  method  of  growing  onions  of  largest  size 
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Thousands  of  farmers  and  gardeners  and  many  experiment 
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5x7  inches.  140  pages.  Cloth $o.$r 


The  New  Rhubarb  Culture 

A  complete  guide  to  dark  forcing  and  field  culture.  Part 
1— By  J.  E.  MORSE,  the  well-known  Michigan  trucker  and 
originator  of  the  now  famous  and  extremely  profitable  new 
methods  of  dark  forcing  and  field  culture.  Part  II — Compiled 
by  G.  B.  FISKE.  Other  methods  practiced  by  the  most  experi- 
enced market  gardeners,  greenhouse  men  and  experimenters  in 
all  parts  of  America.  Illustrated.  130  pages.  5x7  inches. 
Cloth. $0.50 


Alfalfa 

By  F.  D.  COBURN.  Its  growth,  uses  and  feeding  value. 
The  fact  that  alfalfa  thrives  in  almost  any  soil;  that  without 
reseeding  it  goes  on  yielding  two,  three,  four  and  sometimes 
five  cuttings  annually  for  five,  ten  or  perhaps  100  years;  and 
that  either  green  or  cured  it  is  one  of  the  most  nutritious 
forage  plants  known,  makes  reliable  information  upon  its  pro- 
duction and  uses  of  unusual  interest.  Such  information  is 
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authority.  Illustrated.  164  pages.  5x7  inches.  Cloth.  $0.50 

Ginseng,  Its   Cultivation,    Harvesting,   Market 
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By  MAURICE  G.  KAINS,  with  a  short  account  of  its  histonr 
and  botany.  It  discusses  in  a  practical  way  how  to  begin  with 
either  seed  or  roots,  soil,  climate  and  location,  preparation, 
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larged. Illustrated.  5x7  inches.  Cloth.  .  .  .  $0.50 

Landscape  Gardening 

By  F.  A.  WAUGH,  professor  of  horticulture,  University  of 
Vermont.  A  treatise  on  the  general  principles  governing 
outdoor  art ;  with  sundry  suggestions  for  their  application 
in  the  ccmmoner  problems  of  gardening.  Every  paragraph  is 
short,  terse  and  to  the  point,  giving  perfect  clearness  to  the 
discussions  at  all  points.  In  spite  of  the  natural  difficulty 
of  presenting  abstract  principles  the  whole  matter  is  made 
entirely  plain  even  to  the  inexperienced  reader.  Illustrated. 
152  pages.  5x7  inches.  Cloth $0.50 

Hedges,  Windbreaks,  Shelters  and  Live  Fences 

By  E.  P.  POWELL.  A  treatise  on  the  planting,  growth 
and  management  of  hedge  plants  for  country  and  suburban 
homes.  It  gives  accurate  directions  concerning  hedges ;  how 
to  plant  and  how  to  treat  them ;  and  especially  concerning 
windbreaks  and  shelters.  It  includes  the  whole  art  of  making 
a  delightful  home,  giving  directions  for  nooks  and  balconies, 
for  bird  culture  and  for  human  comfort.  Illustrated.  140 
pages.  5x7  inches.  Cloth.  ......  $0.50 


Farm  Grasses  of  the  United  States  of  America 

By  WILLIAM  JASPER  SPILLMAN.  A  practical  treatise  on 
the  grass  crop,  seeding  and  management  of  meadows  and 
pastures,  description  of  the  best  varieties,  the  seed  and  its 
impurities,  grasses  for  special  conditions,  lawns  and  \awn 
grasses,  etc.,  etc.  In  preparing  this  volume  the  author's  ob- 
ject has  been  to  present,  in  connected  form,  the  main  facts 
concerning  the  grasses  grown  on  American  farms.  Every 
phase  of  the  subject  is  viewed  from  the  farmer's  standpoint. 
Illustrated.  248  pages.  5x7  inches.  Cloth.  .  .  $1.00 


The  Book  of  Corn 

By  HERBERT  MYRICK,  assisted  by  A-  D-  SHAMEL,  E.  A. 
BURNETT,  ALBERT  W.  FULTON,  B.  W.  SNOW  and  other  most 
capable  specialists.  A  complete  treatise  on  tbe  culture, 
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farmers,  dealers  and  others.  Illustrated.  372  pages.  5x7 
inches.  Cloth $1.50 


The   Hop  —  It's  Culture  and  Care,  Maiketing 
and  Manufacture 

By  HERBERT  MYRICK.  A  practical  handbook  on  the  most 
approved  methods  in  growing,  harvesting,  curing  and  sellir/g 
hops,  and  on  the  use  and  manufacture  of  hops.  The  result  of 
years  of  research  and  observation,  it  is  a  volume  destined  to 
be  an  authority  on  this  crop  for  many  years  to  come.  It 
takes  up  every  detail  from  preparing  the  soil  and  laying  out 
the  yard  to  curing  and  selling  the  crop.  Every  line  represents 
the  ripest  judgment  and  experience  of  experts.  Size,  5x8; 
pages,  300;  illustrations,  nearly  150;  bound  in  cloth  and  gold; 
price,  postpaid, $1-50 


)  Tobacco  Leaf 

By  J.  B.  KILLEBREW  and  HERBERT  MYRICK.  Its  Culture 
1  and  Cure,  Marketing  and  Manufacture.  A  practical  hand- 
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operations  in  every  department  of  tobacco  manufacture.  The 
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field,  curing  barn,  packing  house,  factory  and  laboratory.  It 
is  the  only  work  of  the  kind  in  existence,  and  i?  destined  to  be 
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subject  of  tobacco  for  many  years.  506  pages  and  150  original 
engravings.  5x7  inches.  Cloth fa.oa 


Bulbs  and  Tuberous-Rooted  Plants 

By  C.  L.  ALLEN.     A  complete  treatise  on  the  history, 

description,  methods  of  propagation  and  full  directions  for 
the  successful  culture  of  bulbs  in  the  garden,  dwelling  and 
greenhouse.  The  author  of  this  book  has  for  many  years 
made  bulb  growing  a  specialty,  and  is  a  recognized  authority 
on  their  cultivation  and  management.  The  cultural  direc- 
tions are  plainly  stated,  practical  and  to  the  point.  The 
illustrations  which  embellish  this  work  have  been  drawn 
from  nature  and  have  been  engraved  especially  for  this 
book.  312  pages.  5x7  inches.  Cloth,  .  .  .  $1.50 

Fumigation  Methods 

By  WILLIS  G.  JOHNSON.  A  timely  up-to-date  book  on 
the  practical  application  of  the  new  methods  for  destroying 
insects  with  hydrocyanic  acid  gas  and  carbon  bismphid,  the 
most  powerful  insecticides  ever  discovered.  It  is  an  indis- 
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ers, florists,  millers,  grain  dealers,  transportation  companies, 
college  and  experiment  station  workers,  etc.  Illustrated.  313 
pages.  5x7  inches.  Cloth $1.00 

Diseases  of  Swine 

By  Dr.  R.  A.  CRAIG,  Professor  of  Veterinary  Medicine  at 
the  Purdue  University.  A  concise,  practical  and  popular  guide 
to  the  prevention  and  treatment  of  the  diseases  of  swine.  With 
the  discussions  on  each  disease  are  given  its  causes,  symptoms, 
treatment  and  means  of  prevention.  Every  part  of  the  book 
impresses  the  reader  with  the  fact  that  its  writer  is  thoroughly 
and  practically  familiar  with  all  the  details  upon  which  he 
treats.  All  technical  and  strictly  scientific  terms  are  avoided, 
so  far  as  feasible,  thus  making  the  work  at  once  available  to 
the  practical  stock  raiser  as  well  as  to  the  teacher  and  student. 
Illustrated.  5x7  inches.  190  pages.  Cloth $0.75 

Spraying  Crops — Why,  When  and  How 

By  CLARENCE  M.  WEED,  D.  Sc.  The  present  fourth  edition 
has  been  rewritten  and  reset  throughout  to  bring  it  thoroughly 
up  to  date,  so  that  it  embodies  the  latest  practical  information 
gleaned  by  fruit  growers  and  experiment  station  workers.  So 
much  new  information  has  come  to  light  since  the  third  edition 
was  published  that  this  is  practically  a  new  book,  needed  by 
those  who  have  utilized  the  earlier  editions,  as  well  as  by  fruit 
growers  and  farmers  generally.  Illustrated.  136  pages.  5x7 
inches.  Cloth ,  ,  ,  $0.50 


Successful  Fruit  Culture 

By  SAMUEL  T.  MAYNARD.  A  practical  guide  to  the  culti- 
vation and  propagation  of  Fruits,  written  from  the  standpoint 
of  the  practical  fruit  gro\ver  who  is  striving  to  make  his 
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first  and  with  the  practice  afterwards,  as  the  foundation,  prin- 
ciples of  plant  growth  and  nourishment  must  always  remain 
the  same,  while  practice  will  vary  according  to  the  fruit 
grower's  immediate  conditions  and  environments.  Illustrated. 
265  pages.  5x7  inches.  Cloth $1.00 

Plums  and  Plum  Culture 

By  F.  A.  WAUGH.  A  complete  manual  for  fruit  growers, 
nurserymen,  farmers  and  gardeners,  on  all  known  varieties 
of  plums  and  their  successful  management.  This  book  mark? 
an  epoch  in  the  horticultural  literature  of  America.  It  is  a 
complete  monograph  of  the  plums  cultivated  in  and  indigenous 
to  North  America.  It  will  be  found  indispensable  to  the 
scientist  seeking  the  most  recent  and  authoritative  informa- 
tion concerning  this  group,  to  the  nurseryman  who  wishes  to 
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cultivator  who  would  like  to  grow  plums  successfully.  Illus- 
trated. 391  pages.  5x7  inches.  Cloth.  .  .  .  $1.50 

r  ruit  Harvesting,  Storing,  Marketing 

By  F.  A.  WAUGH.  A  practical  guide  to  the  picking,  stor- 
ing, shipping  and  marketing  of  fruit.  The  principal  subjects 
covered  are  the  fruit  market,  fruit  picking,  sorting  and  pack- 
ing, the  fruit  storage,  evaporating,  canning,  statistics  of  the 
fruit  trade,  fruit  package  laws,  commission  dealers  and  dealing, 
cold  storage,  etc.,  etc.  No  progressive  fruit  grower  can  afford 
to  be  without  this  most  valuable  book.  Illustrated.  232  pages. 
5x7  inches.  Cloth $1.00 

Systematic  Pomology 

By  F.  A.  WAUGH,  professor  of  horticulture  and  landscape 
gardening  in  the  Massachusetts  agricultural  college,  formerly 
of  the  university  of  Vermont.  This  is  the  first  book  in  the 
English  language  which  has  ever  made  the  attempt  at  a  com- 
plete and  comprehensive  treatment  of  systematic  pomology. 
It  presents  clearly  and  in  detail  the  whole  method  bv  which 
fruits  are  studied.  The  book  is  suitably  illustrated.  288  pages. 
5x7  inches.  Cloth.  ..,,,,,,  $i.pq 


Feeding  Farm  Animals 

By  Professor  THOMAS  SHAW.  This  book  is  intended  alike 
for  the  student  and  the  farmer.  The  author  has  succeeded  in 
giving  in  regular  and  orderly  sequence,  and  in  language  so 
simple  that  a  child  can  understand  it,  the  principles  that  govern 
the  science  and  practice  of  feeding  farm  animals.  Professor 
Shaw  is  certainly  to  be  congratulated  on  the  successful  manner 
in  which  he  has  accomplished  a  most  difficult  task.  His  book 
is  unquestionably  the  most  practical  work  which  has  appeared 
on  the  subject  of  feeding  farm  animals.  Illustrated.  5^2  x  8 
inches.  Upward  of  500  pages.  Cloth $2.oc 


Profitable  Dairying 

By  C.  L.  Peck.  A  practical  guide  to  successful  dairy  man- 
agement. The  treatment  of  the  entire  subject  is  thoroughly 
practical,  being  principally  a  description  of  the  methods  prac- 
ticed by  the  author.  A  specially  valuable  part  of  this  book 
consists  of  a  minute  description  of  the  far-famed  model  dairy 
farm  of  Rev.  J.  D.  Detrich,  near  Philadelphia,  Pa.  On  this 
farm  of  fifteen  acres,  which  twenty  years  ago  could  not  main- 
tain one  horse  and  two  cows,  there  are  now  kept  twenty-seven 
dairy  cattle,  in  addition  to  two  horses.  All  the  roughage, 
litter,  bedding,  etc.,  necessary  for  these  animals  are  grown  on 
these  fifteen  acres,  more  than  most  farmers  could  accomplish 
on  one  hundred  acres.  Illustrated.  5x7  inches.  200  pages, 
"loth $0.75 

Practical  Dairy  Bacteriology 

By  Dr.  H.  W.  CONN,  of  Wesleyan  University.  A  complete 
exposition  of  important  facts  concerning  the  relation  of  bacteria 
to  various  problems  related  to  milk.  A  book  for  the  class- 
room, laboratory,  factory  and  farm.  Equally  useful  to  the 
teacher,  student,  factory  man  and  practical  dairyman.  Fully 
illustrated  with  83  original  pictures.  340  pages.  Cloth. 
5'/2  x  8  inches $1.25 


Modern    Methods  of  Testing    Milk  and  Milk 
Products 

By  L.  L.  VANSLYKE.  This  is  a  clear  and  concise  discussion 
of  the  approved  methods  of  testing  milk  and  milk  products. 
All  the  questions  involved  in  the  various  methods  of  testing 
milk  and  cream  are  handled  with  rare  skill  and  yet  in  so  plain 
a  manner  that  they  can  be  fully  understood  by  all.  The  book 
should  be  in  the  hands  of  every  dairyman,  teacher-or  student. 
Illustrated.  214  pages.  5x7  inches f  .  $0,75 


Farmer's  Cyclopedia 
of  Agriculture   0   0 

A  Compendium  of  Agricultural  Science  and  Practice 
on  Farm,  Orchard  and  Garden  Crops,  and  the 
Feeding  and  Diseases  of  Farm  Animals 

<B$  BARLEY  VERNON  WILCOX,  Ph.  D 
and  CLARENCE  BEAMAN  SMITH,  M.  S 

Associate  Editors  in  the  Office  of  Experiment  Stations,   United  Slates 
^Department  of  Agriculture. 

Pfl 


HIS  is  a  new,  practical  and  complete  pres- 
entation of  the  whole  subject  of  agricul- 
ture in  its  broadest  sense.  It  is  designed 
for  the  use  of  agriculturists  who  desire 
up-to-date,  reliable  information  on  all 
matters  pertaining  to  crops  and  stock,  but  more 
particularly  for  the  actual  farmer.  The  volume 
contains 

Detailed  directions  for  the  culture  of  every 
important  field,  orchard,  and  garden  crop 

grown  in  America,  together  with  descriptions  of 
their  chief  insect  pests  and  fungous  diseases,  and 
remedies  for  their  control.  It  contains  an  account 
of  modern  methods  in  feeding  and  handling  all 
farm  stock,  including  poultry.  The  diseases  which 
affect  different  farm  animals  and  poultry  are  de- 
scribed, and  the  most  recent  remedies  suggested  for 
controlling  them. 

Every  bit  of  this  vast  mass  of  new  and  useful 
information  is  authoritative,  practical,  and  easily 
found,  and  no  effort  has  been  spared  to  include  all 
desirable  details.  There  are  between  6,000  and  7,000 
topics  covered  in  these  references,  and  it  contains 
700  royal  8vo  pages  and  nearly  500  superb  half- 
tone and  other  original  illustrations,  making  the 
most  perfect  Cyclopedia  of  Agriculture  ever  at- 
tempted. 

Handsomely  bound    in    cloth,  $3.50;   half  morocco 
(Vert}  sumptuous,  $4.50,  postpaid 

PHMPAKlV     439'441  LalayettB  Street,  New  York. 
OUMrANY,          Marqu«tte  Building,  ChicajQ,  Ut 


This  book  is  DUE  on  the  last  date  stamped  below 


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